When I found myself with a browser that I didn't seem to be driving anymore, and adaware, spybot, et al couldn't find anything, someone pointed me to hijackthis. Not being computer literate enough to translate the data it spit out into usable information myself, I posted it on a tech board and was told very quickly what the problem was and how to get rid of it. You might want to give it a try. You can find a review and download it
here