HP, on May 26 2011, announced repleacement of about 162,00 defective notebook battaries duo to fire hazard. And HP suggests HP notebook users to visit its official website to validate if their battaries are affected.
Announcement could be found here:
http://www.cpsc.gov/cpscpub/prerel/prhtml11/11234.html
http://bpr.hpordercenter.com/HBPR/US-en/Default.aspx