2. STOCK-BASED COMPENSATION - Options outstanding and exercisable (Details 4) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended
	Feb. 28, 2014	Nov. 30, 2013	Aug. 31, 2013	May 31, 2013
Range Exercise Prices Options Outstanding Minimum	$ 0.59
Range Exercise Prices Options Outstanding Maximum	$ 2.68
Number of Options Outstanding, Ending (in thousands)	3,065	3,150	3,323	2,956
Weighted Average Remaining Contractual Life (Years) Options Outstanding	4 years 4 months 6 days
Weighted Average Exercise Price Outstanding, Ending	$ 1.26	$ 1.25	$ 1.27	$ 1.79
Number Exercisable Shares (in thousands)	1,852
Weighted Average Remaining Contractual Life (Years) Options Exercisable	3 years 7 months 6 days
Weighted Average Exercise Price Options Excercisable	$ 1.21
Aggregate Intrinsic Value Options Exercisable	$ 2,051
Options Price Range A
Range Exercise Prices Options Outstanding Minimum	$ 0.59
Range Exercise Prices Options Outstanding Maximum	$ 0.97
Number of Options Outstanding, Ending (in thousands)	1,000
Weighted Average Remaining Contractual Life (Years) Options Outstanding	3 years 9 months 4 days
Weighted Average Exercise Price Outstanding, Ending	$ 0.75
Number Exercisable Shares (in thousands)	804
Weighted Average Remaining Contractual Life (Years) Options Exercisable	3 years 6 months
Weighted Average Exercise Price Options Excercisable	$ 0.79
Options Price Range B
Range Exercise Prices Options Outstanding Minimum	$ 1.09
Range Exercise Prices Options Outstanding Maximum	$ 1.42
Number of Options Outstanding, Ending (in thousands)	1,442
Weighted Average Remaining Contractual Life (Years) Options Outstanding	5 years 1 month 10 days
Weighted Average Exercise Price Outstanding, Ending	$ 1.28
Number Exercisable Shares (in thousands)	585
Weighted Average Remaining Contractual Life (Years) Options Exercisable	4 years 4 months 13 days
Weighted Average Exercise Price Options Excercisable	$ 1.29
Options Price Range C
Range Exercise Prices Options Outstanding Minimum	$ 1.73
Range Exercise Prices Options Outstanding Maximum	$ 1.95
Number of Options Outstanding, Ending (in thousands)	461
Weighted Average Remaining Contractual Life (Years) Options Outstanding	3 years 18 days
Weighted Average Exercise Price Outstanding, Ending	$ 1.88
Number Exercisable Shares (in thousands)	361
Weighted Average Remaining Contractual Life (Years) Options Exercisable	2 years 5 months 19 days
Weighted Average Exercise Price Options Excercisable	$ 1.91
Options Price Range D
Range Exercise Prices Options Outstanding Minimum	$ 2.15
Range Exercise Prices Options Outstanding Maximum	$ 2.68
Number of Options Outstanding, Ending (in thousands)	162
Weighted Average Remaining Contractual Life (Years) Options Outstanding	4 years 9 months 29 days
Weighted Average Exercise Price Outstanding, Ending	$ 2.50
Number Exercisable Shares (in thousands)	102
Weighted Average Remaining Contractual Life (Years) Options Exercisable	4 years
Weighted Average Exercise Price Options Excercisable	$ 1.57