I had a similar problem, but it was not a virus. I keep my AV up to date, run Spyware, and Ad-Aware. You do need to get rid of the virii, however they are not necessarily the problem. I think I messed something up by writing to a part of memory that I should not have been touching... or something. Anyway, I just rebooted and it worked. Norton AV is really good about cleaning and it does AV before it installs.

-Cheers-