Problem:

SVCHOST.exe sucking 100% CPU

Solution:

• Stop the automatic updates service
• Download http://go.microsoft.com/fwlink/?LinkId=43264
• Run WindowsUpdateAgent20-x86.exe /wuforce
• Rename C:\windows\software distribution to C:\windows\software distribution.old
• Rename C:\windows\windowsupdate.log to c:\windows\windowsupdate.log.old
• Restart the automatic updates service.

See also:

http://support.microsoft.com/kb/914810
http://support.microsoft.com/kb/916089