Problem with browser's "back" button

[Smoothcat]

Okay, this problem is one that may need to be taken to a spyware forum of some kind, but since this is affecting my GMI viewing I figured I would try it out on here first.

I am by no means a computer expert. I use IE 7; I know it's not as "good" as Firefox but I am not planning to change. About a week ago I had some particularly nasty spyware infect my PC. I believe I have it all cleaned out; I used Spyware Doctor and the last few scans I have run have found nothing. Everything seems to be back to normal, except for when I visit a few sites. Here on GMI, if I go read a topic, when I try to hit the "back" button, nothing happens. If I click the "down" arrow and see the last few pages I browsed, there are nothing but links to what I assume are advertising sites (ex: http://page2ad.googlesyndication.com). Speaking of Google, it seems to happen there too. I'm not getting any kind of pop-up windows on my screen.

I've tried searching for an answer to this problem but haven't really been successful. I don't know how to describe it any better than this. Is there still spyware on my computer? Or is this some other kind of quirky bug? Any help will be greatly appreciated.