Exhibit 12.1

COMPUTATION OF RATIO OF EARNINGS TO FIXED CHARGES

(in thousands)

	For the Year Ended December 31,
	2003			2004			2005			2006			2007
Earnings (loss)-
Loss before income taxes	$	(29,789	)	$	(93,271	)	$	(88,593	)	$	(78,298	)	$	(29,469	)
Add fixed Charges:
Interest expense on indebtedness	$	990		$	4,480		$	6,556		$	8,676		$	10,562
Estimated interest on rental expense		300			1,611			1,948			1,959			1,733
Amortization of deferred closing costs related to convertible notes		156			521			816			827			1,324
Amortization of discount on convertible notes		271			—			—			—			7,649
Total Adjusted Loss	$	(28,072	)	$	(86,659	)	$	(79,273	)	$	(66,836	)	$	(8,201	)
Fixed Charges-
Interest expense on indebtedness	$	990		$	4,480		$	6,556		$	8,676		$	10,562
Estimated interest on rental expense		300			1,611			1,948			1,959			1,733
Amortization of deferred closing costs related to convertible notes		156			521			816			827			1,324
Amortization of discount on convertible notes		271			—			—			—			7,649
Total Fixed Charges	$	1,717		$	6,612		$	9,320		$	11,462		$	21,268
Coverage deficiency	$	(29,789	)	$	(93,271	)	$	(88,593	)	$	(78,298	)	$	(29,469	)