Condensed Statements of Cash Flows (Unaudited) (USD $) In Thousands	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
Cash Flows from Operating Activities:
Net loss	$ (18,616)	$ (11,950)
Adjustments to reconcile net loss to net cash used in operating activities
Loss from disposition of assets	1	3
Stock-based compensation expenses	2,094	2,929
Non-employee stock option expense	1	6
Depreciation expense	373	417
Amortization of investment premiums	59	190
Issuance of common stock for services rendered	38	1
Changes in operating assets and liabilities:
Accounts receivable		4,471
Prepaid expenses and other current assets	424	(601)
Accounts payable, accrued expenses and other liabilities	16	4,346
Deferred revenue		(11,115)
Net cash used in operating activities	(15,610)	(11,303)
Cash Flows from Investing Activities:
Purchases of available-for-sale securities	(1,025)	(8,309)
Proceeds from maturity of available-for-sale securities	17,585
Decrease in restricted cash	102	103
Purchases of property and equipment	(21)	(88)
Net cash provided by (used in) investing activities	16,641	(8,294)
Cash Flows from Financing Activities:
Sale of common stock and warrants, net of issuance costs		14,089
Proceeds from exercise of common stock options and employee stock purchases	47	104
Payments on capital lease	(8)	(15)
Net cash provided by financing activities	39	14,178
Net increase (decrease) in cash and cash equivalents	1,070	(5,419)
Cash and cash equivalents, beginning of period	17,008	25,471
Cash and cash equivalents, end of period	$ 18,078	$ 20,052