EX-5.1

At your request, we have examined the Post-Effective Amendment No. 3 to Registration Statement on Form S-3 (the “Registration Statement”) filed by you (the “Company”) with the Securities and Exchange Commission (“SEC”) on February 12, 2014 in connection with the registration under the Securities Act of 1933, as amended (the “Securities Act”), of an aggregate of (i) 4,521,619 shares (the “Conversion Shares”) of your common stock, no par value per share (the “Common Stock”), issued upon conversion of 794,659 shares of your Series A Convertible Preferred Stock, (ii) 10,028,888 shares of Common Stock (the “Warrant Shares”) issuable upon exercise of outstanding warrants (the “Warrants”) and (iii) 61,302 shares of Common Stock issued upon exercise of a Warrant in July 2011 (the “July 2011 Shares” and, together with the Warrant Shares and the Conversion Shares, the “Shares”). The Shares are accompanied by a Common Stock purchase right (the “Purchase Right”) pursuant to the Shareholder Rights Agreement, dated August 22, 2005, as amended by Amendment No. 1 to Shareholder Rights Agreement dated March 21, 2011, between the Company and Wells Fargo Bank, N.A., as Rights Agent (the “Rights Agreement”). We understand that the Shares are to be sold by the selling shareholders to the public from time to time as described in the Registration Statement.

We have examined originals or copies of those corporate and other records and documents we considered appropriate. In our examination, we have assumed the legal capacity of all natural persons, the genuineness of all signatures, the authenticity of all documents submitted to us as originals, the conformity to original documents of all documents submitted to us as certified, conformed or photostatic copies and the authenticity of the originals of such latter documents. As to any facts material to the opinions expressed herein which were not independently established or verified, we have relied upon oral or written statements and representations of officers and other representatives of the Company.

In connection with the opinions expressed below, we have assumed that, at or prior to the time of delivery of any Shares, (i) the Board of Directors of the Company (the “Board of Directors”) has not modified or rescinded the authorization of the issuance and sale of such Shares, (ii) there has not occurred any change in law affecting the validity or enforceability of such Shares and (iii) with respect to the Warrant Shares, no event has occurred after the date hereof that would result in the Company having an insufficient number of shares of Common Stock authorized and available for issuance. We have also assumed that the terms of the issuance and sale of any Shares have been duly established in conformity with the Amended and Restated Articles of Incorporation of the Company, as amended, as presently in effect (the “Articles of Incorporation”), the Amended and Restated Bylaws of the Company, as amended, as presently in effect (the “Bylaws”) and, in the case of the Warrant Shares, the terms of the Warrants, and that none of the terms of any Shares to be established after the date hereof, nor the issuance and delivery of such Shares, nor the compliance by the Company with the terms of such Shares will violate any applicable law or public policy or result in a violation of any provision of any instrument or agreement then binding upon the Company or any restriction imposed by any court or governmental body having jurisdiction over the Company.

On the basis of such examination, our reliance upon the assumptions in this opinion and our consideration of those questions of law we considered relevant, and subject to the limitations and qualifications in this opinion, we are of the opinion that when certificates representing the Shares in the form required under the California Corporations Code have been duly executed, countersigned, registered and delivered upon payment of the agreed upon consideration therefor, or, in the case of Shares issued in “street name,” the Shares have been entered on the books of the transfer agent and registrar under the names of the nominal owners, the issuance and sale of such Shares will have been duly authorized by all necessary corporate action on the part of the Company, and such Shares will be validly issued, fully paid and nonassessable and the Purchase Rights will be legally valid and binding obligations of the Company, enforceable against the Company in accordance with their terms and under California law, except as may be limited by bankruptcy, insolvency, reorganization, moratorium or similar laws relating to or affecting creditors’ rights generally (including, without limitation, fraudulent conveyance laws), and by general principles of equity including, without limitation, concepts of materiality, reasonableness, good faith and fair dealing and the possible unavailability of specific performance or injunctive relief, regardless of whether considered in a proceeding in equity or at law.

With respect to our opinion as to the Purchase Rights, we have assumed that, at the time of issuance and sale of the Shares, that the Rights Agreement has been duly authorized, executed and delivered by the Rights Agent and that the members of the Board of Directors have acted in a manner consistent with their fiduciary duties as required under applicable law in adopting the Rights Agreement. This opinion does not address the determination a court of competent jurisdiction may make regarding whether the Board of Directors of the Company would be required to redeem or terminate, or take other action with respect to, the Purchase Rights at some future time based on the facts and circumstances existing at that time. In addition, it should be understood that our opinion addresses the Rights Agreement and the Purchase Rights in their entirety and not any particular provision of the Rights Agreement or the Purchase Rights. It should also be understood that it is not settled whether the invalidity of any particular provision of a rights agreement or of rights issued thereunder would result in invalidating such rights in their entirety.

The law covered by this opinion is limited to the present law of the State of California and the State of New York. We express no opinion as to the laws of any other jurisdiction and no opinion regarding the statutes, administrative decisions, rules, regulations or requirements of any county, municipality, subdivision or local authority of any jurisdiction.

We hereby consent to the use of this opinion as an exhibit to the Registration Statement and to the reference to this firm under the heading “Legal Matters” in the prospectus constituting part of the Registration Statement.

Respectfully submitted,

/s/ O’Melveny & Myers LLP

O’MELVENY & MYERS LLP