425

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the

Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): December 14, 2010

PRIMUS TELECOMMUNICATIONS GROUP,

INCORPORATED

(Exact name of registrant as specified in its charter)

Delaware	0-29092	54-1708481
(State or other jurisdiction of incorporation)	(Commission File Number)	(IRS Employer Identification No.)

7901 Jones Branch Drive, Suite 900

McLean, VA 22102

(Address of principal executive offices) (Zip Code)

Registrant’s telephone number, including area code: (703) 902-2800

Not applicable

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

x Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

¨ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

¨ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

¨ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Item 1.01 Entry into a Material Definitive Agreement.

On November 11, 2010, Primus Telecommunications Group, Incorporated, a Delaware corporation, or Primus, announced that it had entered into a definitive merger agreement with Arbinet Corporation, a Delaware corporation, or Arbinet, pursuant to which Primus is to acquire Arbinet in a stock transaction. The Agreement and Plan of Merger, dated November 10, 2010, or the Merger Agreement, by and among Primus, PTG Investments, Inc., a Delaware corporation and a wholly owned subsidiary of Primus, or Merger Sub, and Arbinet contemplates a merger whereby Merger Sub will be merged with and into Arbinet, with Arbinet surviving the merger as a wholly owned subsidiary of Primus.

Primus filed a copy of the Merger Agreement under a Current Report on Form 8-K on November 12, 2010. The parties to the Merger Agreement have subsequently discovered certain ambiguities in need of clarification in the text of the provisions of the Merger Agreement, which ambiguities have since been clarified by Amendment No. 1 to the Agreement and Plan of Merger dated as of December 14, 2010 among Primus, Merger Sub and Arbinet. A copy of Amendment No. 1 to the Agreement and Plan of Merger is being filed as an exhibit to this Report.

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Important Information and Where to Find It

In connection with the proposed merger, Primus Telecommunications Group, Incorporated (“Primus”) will file with the Securities and Exchange Commission (“SEC”) a Registration Statement on Form S-4 that will include a preliminary proxy statement of Primus and Arbinet Corporation (“Arbinet”) that also constitutes a preliminary prospectus of Primus. A definitive joint proxy statement/prospectus will be sent to security holders of both Arbinet and Primus seeking their approval with respect to the proposed merger. Primus and Arbinet also plan to file other documents with the SEC regarding the proposed transaction. INVESTORS AND SECURITY HOLDERS ARE URGED TO CAREFULLY READ THE JOINT PROXY STATEMENT/PROSPECTUS AND OTHER DOCUMENTS FILED WITH THE SEC WHEN THEY BECOME AVAILABLE, BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION. Investors and security holders may obtain a free copy of the joint proxy statement/prospectus (when it becomes available) and other documents filed by Primus and Arbinet with the SEC, without charge, at the SEC’s web site at www.sec.gov. Copies of the joint proxy statement/prospectus, once available, and each company’s SEC filings that will be incorporated by reference in the joint proxy statement/prospectus may also be obtained for free by directing a request to: (i) Primus at tel: +1.703.748.8050, or (ii) Arbinet via Andrea Rose or Jed Repko at Joele Frank, Wilkinson Brimmer Katcher at tel: +1.212.355.4449.

Participants in the Solicitation

Arbinet, Primus, and their respective directors, executive officers and other members of their management and employees may be deemed to be “participants” in the solicitation of proxies from their respective security holders in connection with the proposed merger. Investors and security holders may obtain information regarding the names, affiliations and interests of Primus’s directors, executive officers and other members of its management and employees in Primus’s Annual Report on Form 10-K for the year ended December 31, 2009, which was filed with the SEC on April 5, 2010, and amended in a Form 10-K/A filed with the SEC on April 28, 2010, Primus’s proxy statement for its 2010 annual meeting, which was filed with the SEC on June 14, 2010, and any subsequent statements of changes in beneficial ownership on file with the SEC. Investors and security holders may obtain information regarding the names, affiliations and interests of Arbinet’s directors, executive officers and other members of their management and employees in Arbinet’s Annual Report on Form 10-K for the year ended December 31,

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2009, which was filed with the SEC on March 17, 2010, Arbinet’s proxy statement for its 2010 annual meeting, which was filed with the SEC on April 30, 2010, and any subsequent statements of changes in beneficial ownership on file with the SEC. These documents can be obtained free of charge from the sources listed above. Additional information regarding the interests of these individuals will also be included in the joint proxy statement/prospectus regarding the proposed transaction when it becomes available.

Forward-Looking Statements

This Current Report on Form 8-K includes “forward-looking statements” as defined by the Securities and Exchange Commission. All statements, other than statements of historical fact, included herein that address activities, events or developments that Arbinet or Primus expects, believes or anticipates will or may occur in the future, including anticipated benefits and other aspects of the proposed merger, are forward-looking statements. These forward-looking statements are subject to risks and uncertainties that may cause actual results to differ materially. Risks and uncertainties that could affect forward-looking statements include, but are not limited to, the following: the risk that the acquisition of Arbinet may not be consummated for reasons including that the conditions precedent to the completion of the acquisition may not be satisfied; the possibility that the expected synergies from the proposed merger will not be realized, or will not be realized within the anticipated time period; the risk that Primus’s and Arbinet’s businesses will not be integrated successfully; the possibility of disruption from the merger making it more difficult to maintain business and operational relationships; any actions taken by either of the companies, including, but not limited to, restructuring or strategic initiatives (including capital investments or asset acquisitions or dispositions); the ability to service substantial indebtedness; the risk factors or uncertainties described from time to time in Arbinet’s filings with the Securities and Exchange Commission; and the risk factors or uncertainties described from time to time in Primus’s filings with the Securities and Exchange Commission (including, among others, those listed under captions titled “Management’s Discussion and Analysis of Financial Condition and Results of Operations — Liquidity and Capital Resources — Short- and Long-Term Liquidity Considerations and Risks;” “— Special Note Regarding Forward-Looking Statements;” and “Risk Factors” in Primus’s annual report on Form 10-K and quarterly reports on Form 10-Q) that cover matters and risks including, but not limited to: (a) a continuation or worsening of global recessionary economic conditions, including the effects of such conditions on our customers and our accounts receivables and revenues; (b) the general fluctuations in the exchange rates of currencies, particularly any strengthening of the United States dollar relative to foreign currencies of the countries where we conduct our foreign operations; (c) the possible inability to raise additional capital or refinance indebtedness when needed, or at all, whether due to adverse credit market conditions, our credit profile or otherwise; (d) a continuation or worsening of turbulent or weak financial and capital market conditions; (e) adverse regulatory rulings or changes in the regulatory schemes or requirements and regulatory enforcement in the markets in which we operate and uncertainty regarding the nature and degree of regulation relating to certain services; and (f) successful implementation of cost reduction efforts. Readers are cautioned not to place undue reliance on forward-looking statements, which speak only as of their dates. Except as required by law, neither Arbinet nor Primus intends to update or revise its forward-looking statements, whether as a result of new information, future events or otherwise.

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Item 9.01 Financial Statements and Exhibits.

(d) Exhibits.

Exhibit No.	Description
2.1	Amendment No. 1 to the Agreement and Plan of Merger, dated as of December 14, 2010, by and among Primus Telecommunications Group, Incorporated, PTG Investments, Inc. and Arbinet Corporation.

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

	PRIMUS TELECOMMUNICATIONS GROUP, INCORPORATED
Dated: December 15, 2010	By:	/s/ Thomas D. Hickey
	Name:	Thomas D. Hickey
	Title:	Secretary and General Counsel

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EXHIBIT INDEX

Exhibit No.	Description
2.1	Amendment No. 1 to the Agreement and Plan of Merger, dated as of December 14, 2010, by and among Primus Telecommunications Group, Incorporated, PTG Investments, Inc. and Arbinet Corporation.

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EX-2.1

Exhibit 2.1

AMENDMENT NO. 1 TO THE

AGREEMENT AND PLAN OF MERGER

This Amendment No. 1 (this “Amendment”) dated as of December 14, 2010 to the Agreement and Plan of Merger dated November 10, 2010 (the “Merger Agreement” or the “Agreement”) by and among Primus Telecommunications Group, Incorporated, a Delaware corporation (“Parent”), PTG Investments, Inc., a Delaware corporation and a direct wholly owned subsidiary of Parent (“Merger Sub”), and Arbinet Corporation, a Delaware corporation (the “Company”).

Whereas, Parent, Merger Sub and the Company have discovered certain ambiguities in need of clarification in the text of the provisions of the Merger Agreement and desire to amend the Merger Agreement to make such clarifications.

Now, therefore, in consideration of the mutual promises contained herein, the benefits to be derived by each party hereunder and other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, Parent, Merger Sub and the Company agree as follows:

AGREEMENT:

Section 1.1 Definitions; References. Unless otherwise specifically defined herein, each term used herein shall have the meaning assigned to such term in the Merger Agreement. Each reference to “hereof,” “herein” and “hereunder” and words of similar import when used in the Merger Agreement shall refer to the Merger Agreement, as amended by this Amendment. For purposes of clarity, references to the date of the Agreement, as amended hereby, and references to “the date hereof” and “the date of this Agreement” shall in all instances continue to refer to November 10, 2010.

Section 1.2 Amendment to Section 5.1. The last paragraph of Section 5.1 of the Merger Agreement is hereby amended and restated in its entirety to read as follows:

Notwithstanding any of the foregoing provisions of this Section 5.1, prior to the Closing, the Company may, at its sole option or not at all, either spin-off to its stockholders, or sell to a third party for cash, the Company’s patents, listed under items 3, 4 and 5 of Schedule 3.16(b), and any rights arising from such patents (any sale to a third party for cash is referred to herein as the “IP Sale”), provided, that (x) any spin-off or the IP Sale shall not result in any residual liability to the Company or any Company Subsidiary (other than costs, fees, expenses and Taxes taken into account as set forth in the following clause (y)), (y) all transaction costs, fees and expenses (which for purposes of clarity shall exclude the appraiser’s fees contemplated in the following clause (z)) and the gross Tax liabilities of the Company (except to the extent offset by net operating losses) attributable to any such spin-off or IP Sale shall not exceed $350,000 in the aggregate and (z) in connection with any such spin-off, the Company shall have obtained an appraisal, from an independent third party appraiser, of the value of such patents and rights subject to such spin-off, and such valuation shall be used for all related Tax reporting purposes. For the avoidance of doubt, the only assets of the Company and any

Company Subsidiary that may be spun-off or sold pursuant to this paragraph of Section 5.1 are the Company’s patents listed under items 3, 4 and 5 of Schedule 3.16(b) and the rights arising from such patents. The amount of the proceeds from the IP Sale, after deduction for all related transaction costs, fees and expenses and gross Tax liabilities attributable to the IP Sale, will either, at the Company’s sole discretion, be (i) distributed to the Company’s stockholders prior to the Closing or (ii) added, dollar for dollar, to the Aggregate Cash-Value Merger Consideration. Prior to the consummation of any such spin-off of the Company’s patents or any IP Sale, the Company shall have first granted to Parent (for its benefit, and the benefit of its affiliates and assignees of the rights under such license) a royalty-free, worldwide, assignable (on a non-exclusive basis) and perpetual license and right to use any and all such patents and associated rights, provided, that in the course of the negotiation, drafting and creation of such license agreement and the documents that will effectuate the spin-off or the IP Sale, the Company shall keep Parent apprised of the status of such negotiation, drafting and creation of such documents, and, among other things, shall promptly provide all drafts of such documents and take into consideration, in good faith, any comments received from Parent with respect to such documents. As part of such license agreement, to the extent legally possible, the Parent and its affiliates and assignees of the rights under such license shall be deemed to have had the right to use such patents and associated rights since the creation of each of such patents and its associated rights.

Section 1.3 Amendment to Section 9.4. The last sentence of the definition of Company Material Adverse Effect in Section 9.4(g) of the Merger Agreement is hereby amended and restated in its entirety to read as follows:

Notwithstanding any of the foregoing, it shall constitute a Company Material Adverse Effect if the sum of the Cash and Cash Equivalents of the Company and the Company Subsidiaries on a consolidated basis and the Marketable Securities, as of the Determination Date, as contemplated by Section 6.13, less (x) all indebtedness then outstanding and (y) all unpaid transaction costs, fees and expenses and gross Tax liabilities of the Company (except to the extent offset by net operating losses) attributable to any IP Sale or any spin-off of the Company’s patents as contemplated by the last paragraph of Section 5.1, and after taking into account the provisions of Section 5.3 (including the adjustments contemplated therein), is less than $9,500,000 (provided that such $9,500,000 shall be reduced by the actual transaction costs, fees and expenses and gross Tax liabilities of the Company (except to the extent offset by net operating losses) attributable to any IP Sale or any spin-off of the Company’s patents as contemplated by the last paragraph of Section 5.1 that have been incurred and actually paid, provided in no event shall more than $350,000 be subtracted from such $9,500,000), excluding all costs incurred by the Company in connection with the Merger and the transactions contemplated by this Agreement, which excluded costs include all legal fees, banker fees, accounting fees, the appraiser’s fees for the appraisal required under clause (z) of the last paragraph of Section 5.1, and other professional services fees.

Section 1.4 No Further Amendment. Except as expressly amended hereby, the Merger Agreement is in all respects ratified and confirmed and all the terms, conditions, and provisions thereof shall remain in full force and effect.

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Section 1.5. Effect of Amendment. This Amendment shall form a part of the Merger Agreement for all purposes, and each party thereto and hereto shall be bound hereby. From and after the execution of this Amendment by the parties hereto, any reference to the Merger Agreement shall be deemed a reference to the Merger Agreement as amended hereby. This Amendment shall for all purposes be deemed to be in full force and effect from and after the original execution of the Merger Agreement by the parties thereto.

Section 1.6 Headings. The descriptive headings contained in this Amendment are included for convenience of reference only and shall not affect in any way the meaning or interpretation of this Amendment.

Section 1.7 Counterparts. This Amendment may be executed in one or more counterparts, and by the different parties hereto in separate counterparts, each of which when executed shall be deemed to be an original but all of which taken together shall constitute one and the same agreement.

Section 1.8 Governing Law; Jurisdiction and Venue. This Amendment shall be governed by, and construed in accordance with, the laws of the State of Delaware applicable to contracts executed in and to be performed in that state. All actions and proceedings arising out of or relating to this Amendment shall be heard and determined in the Delaware Court of Chancery or a federal district court located in Delaware. Each of Parent, Merger Sub and the Company hereby irrevocably and unconditionally consents to submit to the exclusive jurisdiction of the Delaware Court of Chancery or a federal district court located in Delaware for any litigation arising out of or relating to this Amendment and the transactions contemplated hereby (and agrees not to commence any litigation relating thereto except in such court), waives any objection to the laying of venue of any such litigation in the Delaware Court of Chancery or a federal district court located in Delaware and agrees not to plead or claim that such litigation brought therein has been brought in any inconvenient forum.

Section 1.9 Waiver of Jury Trial. EACH OF PARENT, MERGER SUB AND THE COMPANY HEREBY IRREVOCABLY WAIVES, TO THE FULLEST EXTENT PERMITTED BY LAW, ALL RIGHTS OF TRIAL BY JURY IN ANY ACTION, PROCEEDING, OR COUNTERCLAIM (WHETHER BASED UPON CONTRACT, TORT OR OTHERWISE) ARISING OUT OF OR RELATING TO THIS AMENDMENT OR ANY OF THE TRANSACTIONS CONTEMPLATED HEREBY.

Section 1.10 Severability. If any term or other provision of this Amendment is invalid, illegal or incapable of being enforced by any rule of law or public policy, all other conditions and provisions of this Amendment shall nevertheless remain in full force and effect so long as the economic or legal substance of the transactions contemplated hereby is not affected in any manner materially adverse to any party. Upon such determination that any term or other provision is invalid, illegal or incapable of being enforced, the parties hereto shall negotiate in good faith to modify this Amendment so as to effect the original intent of the parties as closely as possible in a mutually acceptable manner in order that the transactions contemplated hereby be consummated as originally contemplated to the fullest extent possible.

[signature page follows]

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IN WITNESS WHEREOF, Parent, Merger Sub and the Company have caused this document to be executed as of the date first written above by their respective officers thereunto duly authorized.

PRIMUS TELECOMMUNICATIONS GROUP, INCORPORATED
By:	/s/ Peter D. Aquino
	Name:	Peter D. Aquino
	Title:	Chairman, Chief Executive Officer and
		President
PTG INVESTMENTS, INC.
By:	/s/ Peter D. Aquino
	Name:	Peter D. Aquino
	Title:	President
ARBINET CORPORATION
By:	/s/ Shawn F. O’Donnell
	Name:	Shawn F. O’Donnell
	Title:	Chief Executive Officer and President