Finally Microsoft released this fix to the public (without the need to call support first)
If you use a computer that is running Microsoft Windows XP with Service Pack 2 (SP2), Microsoft Windows XP Tablet PC Edition 2005, or Microsoft Windows XP Media Center Edition 2005, when you try to put the computer in hibernation, the computer occasionally does not hibernate.
Get more infos and the fix at Microsoft.com
Source : Bink.nu
