My uneducated guess is that you already have some script running, or a cookie accessing something. I'd clear out history and all cookies, then run all your virus, anti spyware programs to try to clean it up.
My wife was getting those for a while, she never even clicked anything, and eventually nothing worked. Had to take it in and get it cleaned. Cost almost as much as a new laptop.
Thanks. I hate clearing out cookies because it makes signing in to sites a nuisance, but I guess I'll have to do it.