What version of Windows and what SP level?
If an older SP2 level of XP, there is a solution on the MS Support site:
http://support.microsoft.com/kb/916261
If Vista, the Vistaheads site has this this solution:
http://www.vistaheads.com/forums/mic...c-updates.html
Other sites have also mentioned running Malwarebytes then trying after getting the PC to a "clean" state.
Might want to give them a try before reverting to a previous system restore point.