PROSPECTUS SUPPLEMENT NO. 2 DATED APRIL 11, 2006 Filed Pursuant to Rule 424(b)(3) and (c)

(To Prospectus dated March 24, 2006) Registration No. 333-132718

$115,000,000

2% Convertible Senior Subordinated Notes due 2025

and 3,908,241 Shares of Common Stock

Issuable Upon Conversion of the Notes

       This Prospectus Supplement relates to resales by selling securityholders of our 2% Convertible Senior Subordinated Notes due 2025 and shares of our common stock into which the notes are convertible.

      This Prospectus Supplement must be read in conjunction with the Prospectus dated March 24, 2006 (the “Prospectus”).

      SEE “RISK FACTORS” BEGINNING ON PAGE 5 OF THE PROSPECTUS, AS THEY MAY BE MODIFIED AND INCORPORATED BY REFERENCE, TO READ ABOUT FACTORS YOU SHOULD CONSIDER BEFORE BUYING THE NOTES OR OUR COMMON STOCK.

      NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR DETERMINED IF THIS PROSPECTUS IS TRUTHFUL OR COMPLETE. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

The date of this Prospectus Supplement is April 11, 2006

SELLING SECURITYHOLDERS

      The information in the table appearing in the Prospectus under the heading “Selling Securityholders” is superseded by the information appearing in the following table based on information provided to us by the selling securityholders as of April 10, 2006:

	Principal				Number of
	Amount of		Number of		Shares of
	Notes		Shares of		Common		Principal		Number of
	Beneficially		Common		Stock Issuable		Amount of		Shares of		Percentage of
	Owned Prior		Stock		Upon		Notes		Common Stock		Common Stock
	to the		Beneficially		Conversion of		Beneficially		Beneficially		Outstanding
	Offering and		Owned Prior		the Notes That		Owned Upon		Owned Upon		Upon
	That May		to the		May be		Completion of		Completion of		Completion of
Selling Securityholder	be Offered		Offering(1)		Offered(2)		the Offering(3)		the Offering(3)		the Offering(4)
Allstate Insurance Company(5)	$	1,500,000		50,977		50,977		—		—		—
Aristeia International Limited	$	11,000,000		373,831		373,831		—		—		—
Aristeia Partners LP	$	1,500,000		50,977		50,977		—		—		—
Citadel Equity Fund Ltd.(5)	$	15,000,000		509,770		509,770		—		—		—
Fore Convertible Master Fund, Ltd.	$	15,000,000		509,770		509,770		—		—		—
Fore Erisa Fund, Ltd.	$	2,500,000		84,961		84,961		—		—		—
Fore Multi Strategy Master Fund, Ltd.	$	6,000,000		203,908		203,908		—		—		—
Forest Fulcrum Fund, LP(6)	$	229,000		7,782		7,782		—		—		—
Forest Global Convertible Fund, Limited, Class A-5	$	655,000		22,259		22,259		—		—		—
Forest Multi-Strategy Master Fund SPC, on behalf of its Multi-Strategy Segregated Portfolio	$	345,000		11,724		11,724		—		—		—
Grace Convertible Arbitrage Fund, Ltd.	$	3,250,000		110,450		110,450		—		—		—
HFR CA Global Opportunity Master Trust	$	579,000		19,677		19,677		—		—		—
HFR RVA Select Performance Master Trust	$	155,000		5,267		5,267		—		—		—
Inflective Convertible Opportunity Fund, Ltd.	$	2,100,000		71,367		71,367		—		—		—
Inflective Convertible Opportunity Fund, LP	$	850,000		28,886		28,886		—		—		—
Institutional Benchmarks Series — Ivan Segregated Acct. Ltd.	$	600,000		20,390		20,390		—		—		—
JMG Capital Partners, LP	$	7,750,000		263,381		263,381		—		—		—
JMG Triton Offshore Fund, Ltd.	$	7,750,000		263,381		263,381		—		—		—
LDG Ltd.	$	266,000		9,039		9,039		—		—		—
Lyxor/ Forest Fund Ltd.	$	878,000		29,838		29,838		—		—		—
Lyxor/ Inflective Convertible Opportunity Fund, Ltd.	$	750,000		25,488		25,488		—		—		—
Man Mac 1, Ltd.	$	6,000,000		203,908		203,908		—		—		—
MSS Convertible Arbitrage c/o TQA Investors	$	70,000		2,378		2,378		—		—		—
Nomura Securities International(6)	$	4,000,000		135,938		135,938		—		—		—
SG Cowen, LLC(6)	$	2,000,000		67,969		67,969		—		—		—

1

	Principal				Number of
	Amount of		Number of		Shares of
	Notes		Shares of		Common		Principal		Number of
	Beneficially		Common		Stock Issuable		Amount of		Shares of		Percentage of
	Owned Prior		Stock		Upon		Notes		Common Stock		Common Stock
	to the		Beneficially		Conversion of		Beneficially		Beneficially		Outstanding
	Offering and		Owned Prior		the Notes That		Owned Upon		Owned Upon		Upon
	That May		to the		May be		Completion of		Completion of		Completion of
Selling Securityholder	be Offered		Offering(1)		Offered(2)		the Offering(3)		the Offering(3)		the Offering(4)
Sphinx Convertible Arbitrage SPC	$	242,000		8,224		8,224		—		—		—
Sphinx Fund c/o TQA Investors	$	275,000		9,345		9,345		—		—		—
TQA Master Fund, Ltd.	$	2,836,000		96,380		96,380		—		—		—
TQA Master Plus Fund, Ltd.	$	1,000,000		33,984		33,984		—		—		—
UBS Securities LLC(6)(7)	$	1,724,000		58,589		58,589		—		—		—
Vicis Capital Master Fund	$	5,000,000		169,923		169,923		—		—		—
Zurich Institutional Benchmark Master Fund	$	553,000		18,793		18,793		—		—		—
All other holders of notes or future transferees, pledges, donees, assignees or successors of any such holders(8)(9)	$	12,643,000		429,668		429,668		—		—		—

(1)	Shares in this column include shares of common stock issuable upon conversion of the notes.
(2)	Assumes conversion of all of the securityholders’ notes at a conversion rate of 33.9847 shares of common stock per $1,000 principal amount of notes. This conversion rate is subject to adjustment, however, as described under “Description of the Notes — Conversion Rights.” As a result, the number of shares of common stock issuable upon conversion of the notes may increase or decrease in the future.
(3)	Assumes that each selling securityholder will sell all of the notes and common stock owned by the selling securityholder and covered by this prospectus.
(4)	Based upon 56,827,114 shares of common stock which is the number of shares of common stock outstanding as of March 7, 2006.
(5)	With respect to selling securityholders that are affiliates of broker-dealers, such entities have represented to us that they acquired their notes or underlying common stock in the ordinary course of business and, at the time of the purchase of the notes or the underlying common stock, such selling securityholders had no agreements or understandings, directly or indirectly, with any person to distribute the notes or underlying common stock. To the extent that we become aware that such entities did not acquire their notes or underlying common stock in the ordinary course of business or did have such an agreement or understanding, we will file a supplement to the prospectus to designate such affiliate as an “underwriter” within the meaning of the Securities Act.
(6)	This selling securityholder has identified itself as a registered broker-dealer and, accordingly, it is deemed to be, under the interpretations of the SEC, an “underwriter” within the meaning of the Securities Act. Please see “Plan of Distribution” for required disclosure regarding these selling securityholders.
(7)	UBS Securities LLC was the initial purchaser of the notes; however, the notes registered herein were acquired from a qualified institutional buyer following the initial issuance by the Company.
(8)	Information about other selling securityholders will be set forth in prospectus supplements or amendments, if required.
(9)	Assumes that any other holders of the notes or any future pledges, donees, assignees, transferees or successors of or from any other such holders of the notes, do not beneficially own any shares of common stock other than the common stock issuable upon conversion of the notes at the initial conversion rate.

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