In mid-February, Microsoft halted automatic distribution of one of its Windows patches, blaming the interaction of the patch with already-present malware on users’ systems for a rash of blue-screen-of-death reports among XP users.

On March 2, Microsoft began redistributing that patch, and reiterated plans to release in a few weeks a rootkit detector aimed at removing the Alureon rootkit from users systems.

http://blogs.zdnet.com/microsoft/?p=5459