Posted 19 October 2010 - 01:31 PM
Had this same problem myself. Been fighting it for two days. Seems like someone hijacked a friends Facebook account and sent a message through that with malware attached. After much searching and trial and error today I came across a forum where someone with the same problem tried AVG anti-virus software with great success. I figured there was not much to loose so I did a search, found the site and downloaded the free version.
Before installation you're required to uninstall Microsoft Security Essentials. Since two MSE scans did no good, and figuring I could always install it again I went ahead and did the uninstall. I then installed AVG and first ran the "Rootkit" since that had been mentioned somewhere. It found nothing and I was prompted to run an initial optimization scan, i.e. the scan that you're supposed to run the first time you use it. It took a little time, which was to be expected, but came up with one threat which it "healed". Although I only did all this about 20 minutes ago my computer seems to be running at it's former speed, I'm not getting any error messages, and the really annoying unwanted navigation to advertising sites has stopped. In other words I think it's fixed.
The download is free and it seems to work great so maybe you should give it a try. AVG also does a fee based upgrade but unless you do a lot of stuff on Facebook or Twitter it appears that pretty much everything you need is in the free version.