I had that, it’s not a virus. It’s a new AIM beta thing. It comes up to a page and it has all of your buddies and their infos and away messages. Its quite nifty. I had that problem too, I guess it was just a preview.
If you’re using Windows XP, did you try deleteing your account (and saving you files) and creating a new one? Or have you tried AIM on a differnent user? Maybe that will help.