STATEMENTS OF CASH FLOWS (USD $) In Thousands	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010
Operating Activities:
Net loss:	$ (12,446)	$ (19,200)
Reconciliation of net loss to net cash used in operating activities:
Change in fair value of warrant liability	(1,237)	(1,638)
Depreciation and amortization	788	633
Amortization of net premiums on short-term investments	231	66
Impairment of property and equipment	0	127
Deferred rent	(168)	(131)
Non-cash stock-based compensation	1,135	509
Changes in operating assets and liabilities:
Accounts receivables	(1,778)	(98)
Unbilled receivables	(2,020)	0
Prepaid expenses and other current assets	(636)	843
Accounts payable and accrued expenses	(3,808)	258
Deferred revenue	2,500	(96)
Net cash used in operating activities	(17,439)	(18,727)
Investing Activities:
Capital expenditures	(178)	(712)
Proceeds from maturities of short-term investments	15,375	900
Purchases of short-term investments	(1,082)	(14,199)
Net cash provided by (used in) by investing activities	14,115	(14,011)
Financing Activities:
Principal payments of notes payable	(40)	(46)
Net proceeds from sales of common stock, net of offering costs of $0.2 million and $0.1 million, respectively	8,280	3,060
Proceeds from the exercise of stock options	115	413
Net cash provided by financing activities	8,355	3,427
Net increase (decrease) in cash and cash equivalents	5,031	(29,311)
Cash and cash equivalents at beginning of period	8,061	38,757
Cash and cash equivalents at end of period	13,092	9,446
Supplemental disclosure of non-cash activities:
Equipment purchases included in accounts payable	$ 34	$ 297