Prospectus Supplement No. 5
(To Prospectus dated August 22, 2006)
  Filed Pursuant to Rule 424(b)(3) and Rule 424(b)(7)
Registration Number 333-136819
3.75% Convertible Subordinated Notes Due 2026
and the Common Stock Issuable Upon Conversion of the Notes
     This prospectus supplement relates to the resale by selling security holders of our 3.75% Convertible Subordinated Notes Due 2026 and the shares of our common stock issuable upon conversion of the notes.
     This prospectus supplement should be read in conjunction with, and may not be delivered or utilized without, the original prospectus dated August 22, 2006, Supplement No. 1 to such prospectus dated August 31, 2006, Supplement No. 2 to such prospectus dated September 14, 2006, Supplement No. 3 to such prospectus dated September 28, 2006 and Supplement No. 4 to such prospectus dated November 1, 2006. The terms of the notes are set forth in the original prospectus.
Investing in these securities involves risks. See “Risk Factors” beginning on page 10 of the prospectus.
     Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the notes or the shares of common stock issuable upon conversion of the notes or determined if the prospectus or this prospectus supplement is truthful or complete. Any representation to the contrary is a criminal offense.
The date of this prospectus supplement is January 11, 2007.



     The information in the table appearing under the heading “Selling Security Holders” in the prospectus is amended by adding the information below with respect to persons not previously listed in the prospectus and by supplementing the information with respect to other persons previously listed in the prospectus that are listed below. This information was furnished to us by the selling security holders listed below on or before January 10, 2007.
     Based on information provided by the selling security holders, none of the selling security holders has held any position or office or has had any material relationship with us within the past three years.
    Principal       Shares of           Shares of    
    Amount of       Common           Common    
    Notes       Stock   Shares of   Stock   Percentage
    Beneficially   Percentage   Beneficially   Common   Beneficially   of Common
    Owned and   of Notes   Owned Prior   Stock   Owned After   Stock
Name   Offered   Outstanding   Offering   Offered   Offering   Outstanding
Nicholas Applegate Capital Management U.S. Convertible Mutual Fund(1)
  $ 870,000     *     38,822       38,822     ___   ___
*   Less than one percent
     (1) Nicholas-Applegate Capital Management LLC (“Nicholas-Applegate”) is an investment adviser. Nicholas-Applegate is an affiliate of Nicholas-Applegate Securities LLC, a limited purpose broker-dealer. As the investment adviser, Nicholas-Applegate has voting and dispositive power over the securities held by this security holder. Horacio A. Valeiras, in his capacity as the Chief Investment Officer of Nicholas-Applegate, has oversight authority over all portfolio managers of Nicholas-Applegate.