Hopefully you don't still have the problem. It sounds like this fake product designed to get you to download and pay for a service. It showed up on a friend's computer on 9/28/2010. Massive nastiness, including disabling task manager.
I haven't followed the instructions below, so I can't vouch for them, but this pretty well describes my friend's system's infection and might be what you have.
microsoft security essentials will not download as wizard stops and say it can ot continue. i have the latest version of explorer..what's wrong..please help