Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Operating activities:
Net loss	$ (5,167)	$ (6,158)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	872	1,073
Provision for doubtful accounts and other adjustments to accounts receivable	72	145
Provision for excess and obsolete inventory	22	35
Non-cash compensation related to stock options, ESPP and restricted stock	717	905
Change in operating accounts:
Accounts receivable	449	(996)
Inventories	(22)	8
Prepaid expenses and other assets	136	171
Accounts payable and accrued liabilities	(677)	931
Net cash used in operating activities	(3,598)	(3,886)
Investing activities:
Capital expenditures	(15)	(90)
Sales (purchases) of short-term investments	453	(2,167)
Net cash provided by (used in) investing activities	438	(2,257)
Financing activities:
Cash received from stock sale for employee stock purchase plan	11	21
Cash received from exercise of stock options	6
Net cash provided by financing activities	17	21
Net decrease in cash and cash equivalents	(3,143)	(6,122)
Cash and cash equivalents, beginning of period	11,763	18,873
Cash and cash equivalents, end of period	8,620	12,751
Supplemental disclosures of cash flow information:
Cash paid for income taxes	$ 15	$ 71