diogenysos: Sounds like an update glitch from Microsoft then. I'm only saying that as one of their updates caused conflicts with our internet security software. I'd go through any recent updates from them and uninstall the latest... or give them a call and get advice!!

The other option is... http://www.combofix.org/ .......... It's a desktop run program that scans deep and gives a full report on the likes of registry issues. But make sure ( as prompted) you use the back up option first.

But I'd lean towards it being an update conflict.