Firefox redirected against my will to adware

Twice in the last week, I have been surfing using Firefox 3.5.5, when out of the blue all but one of the open tabs close, a pop-up warns that my computer is infected and I must download/scan using such-and-such program (most recently, iGuard AntiSpyware or something like that) and the open tab redirects to a page that's meant to look like a scan of my hard drive is underway, finding trojans and other bad stuff on my drives. The pop-ups and scan tabs are hard to make go away -- they don't typically just close when I click on the top-right Xs, they usually result in more pop-ups/redirects.

I have gone through the READ & RUN ME FIRST Malware Removal Guide and Windows XP Cleaning Procedures. I do not know if I still have problems, as I can only tell when the undesired redirects occur...But my SAS, Malwarebytes Anti-Malware, and RootRepeal scans didn't seem to turn up anything and I don't know what the MGTools found...ComboFix is currently unavailable...I took a look at the similar threads and didn't quite find my problem...I have attached the requested logs.

I also want to note that Chaslang's post in the Read & Run Me First/Malware Removal Guide or Windows XP Cleaning Procedures, or one of the pages linked therein, states not to use msconfig to control startups (and that CCleaner's StartUp Tool simply uses msconfig, so not to use it), but that Major Attitude's "Basic computer maintenance..." page does suggest using CCleaner's StartUp Tool... Which should I go by?

Thank you for your time and attention!

 

AntiVir was the first such pop-up/redirect. iGuard was second.