STOCK-BASED COMPENSATION (Tables)

6 Months Ended

Jun. 30, 2013

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2013		2012		2013		2012

Option Plan Shares
Risk-free interest rates	0.94%		0.82%		0.94% - 1.15%		0.82% - 0.84%
Expected term (in years)	6		6		6		6
Expected volatility	82.9%		87.1%		82.9% - 84.0%		87.1% - 91.6%
Dividend yield	0%		0%		0%		0%
Weighted average fair value per share of options granted during the period	$	6.55	$	7.38	$	7.66	$	6.86

ESPP Shares
Risk-free interest rates	0.11% - 0.20%		0.19% - 0.27%		0.11% - 0.20%		0.19% - 0.27%
Expected term (in years)	0.5-2		0.5 - 2		0.5-2		0.5 - 2
Expected volatility	39.1% - 45.6%		39.6% - 54.9%		39.1% - 45.6%		39.6% - 54.9%
Dividend yield	0%		0%		0%		0%
Weighted average fair value per share of stock purchase rights granted during the period	$	2.80	$	3.47	$	2.80	$	3.47

Summary of stock option activity under the Stock Plans

					Weighted
			Weighted		Average
			Average		Remaining	Aggregate
			Exercise		Contractual	Intrinsic
Options	Shares		Price		Term (Years)	Value (1)
(Aggregate intrinsic value in thousands)

Outstanding, January 1, 2013	6,181,996		$	2.62	6.6	$	49,439
Granted	240,570		$	10.72
Exercised	(98,869	)	$	4.99
Forfeited	(74,250	)	$	8.67
Outstanding, June 30, 2013	6,249,447		$	2.83	6.2	$	69,266

Exercisable, June 30, 2013	5,205,858		$	1.84	5.8	$	62,849

Vested and expected to vest June 30, 2013	6,220,586		$	2.84	6.2	$	69,089

(1)The aggregate intrinsic value of options outstanding, exercisable and vested and expected to vest is calculated as the difference between the exercise price of the underlying options and the market price of the Company’s common stock for options that had exercise prices that were lower than the $13.91 market price of the Company’s common stock at June 30, 2013. The total intrinsic value of options exercised during the six months ended June 30, 2013 was $0.5 million. The total intrinsic value of options exercised during the six months ended June 30, 2012 was $3.4 million.

Summary of restricted stock activity under the Stock Plans

			Weighted
	Restricted		Average Grant
	Shares		Date Fair Value
Outstanding, January 1, 2013	813,955		$	8.51
Granted	581,124		$	10.77
Released	(166,843	)	$	8.63
Forfeited	(352,836	)	$	9.45
Outstanding, June 30, 2013	875,400		$	9.61