Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Oct. 31, 2011	Oct. 31, 2010
Cash flows from operating activities:
Net loss	$ (5,895)	$ (7,459)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,213	1,404
Accretion of interest on convertible note payable		83
Loss on disposal of purchased intangibles and property and equipment	63
Stock-based compensation expense	174	742
Amortization of purchased intangibles	40	40
Changes in assets and liabilities:
Accounts receivable, net of allowance for doubtful accounts	268	(190)
Inventories	52	365
Other current assets	(70)	272
Income taxes payable	7	16
Accounts payable	403	288
Accrued expenses and other accrued liabilities	(80)	(694)
Deferred revenue	705	(242)
Net cash used in operating activities	(3,120)	(5,375)
Cash flows from investing activities:
Purchases of property and equipment	(67)	(22)
Proceeds from sale of purchased intangibles	234
Purchases of available for sale investments	(4,320)	(3,360)
Sales and maturities of available for sale investments	4,320	5,520
Net cash provided by investing activities	167	2,138
Cash flows from financing activities:
Proceeds from employee stock plan issuances	38	58
Net cash provided by financing activities	38	58
Net decrease in cash and cash equivalents	(2,915)	(3,179)
Cash and cash equivalents, beginning of period	24,062	29,634
Cash and cash equivalents, end of period	$ 21,147	$ 26,455