I have had trouble with IE homepage changing on it's own...from: yahoo to:"awesomehomepage.com" say's that it is ad's from Google. I went to the Internet Options & changed it there but it changes itself to this homepage instead of Yahoo's, no matter what I do it keeps changing itself. I just ran a complete virus scan & nothing came up (thank goodness!).
Try installing spybot and Adaware and do full scans with them. Ads will be missed by a virus checker. Dont forget to download the latest updates for both the programs and windows too! Hope that helps
Gerryh