STOCK-BASED COMPENSATION (Details 2) (Warrant [Member], USD $)	12 Months Ended
	May 31, 2013	May 31, 2012	May 31, 2011	May 31, 2010	May 31, 2009	May 31, 2008	May 31, 2007
Warrant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balance (in shares)	5,895,945	5,235,945	11,735,004	11,735,004	10,044,916	9,048,240	4,392,874
Balance (in dollars per shares)	$ 0.50	$ 0.50	$ 0.63	$ 0.63	$ 0.84	$ 0.88	$ 0.84
Granted (in shares)	0	660,000	0	0	4,022,225	1,821,676	4,655,366
Granted (in dollars per shares)	$ 0	$ 0.035	$ 0	$ 0	$ 0.25	$ 0.85	$ 0.93
Exercised (in shares)	0	0	0	0	0	0	0
Exercised (in dollars per shares)	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Expired or cancelled (in shares)	(3,545,865)	0	(6,499,057)	0	(2,332,137)	(825,000)	0
Expired or cancelled (in dollars per shares)	$ 0.70	$ 0	$ 0.70	$ 0	$ 0.85	$ 0.67	$ 0
Balance (in shares)	2,350,080	5,895,945	5,235,945	11,735,004	11,735,004	10,044,916	9,048,240
Balance (in dollars per shares)	$ 0.19	$ 0.50	$ 0.50	$ 0.63	$ 0.63	$ 0.84	$ 0.88