Effect of Spoofing from 85.255.115.221 on Firefox 2?

I was spoofed from a Google-Search to 85.255.115.221 (instead of produkte24.com) and FF started popping up a Window which wanted to "search for malware". I immediately finished my Firefox session but of course I wasn't able to reproduce the attack (as described in https://www.wilderssecurity.com/showthread.php?t=136452&highlight=85.255.115.221 and https://www.wilderssecurity.com/showthread.php?t=175666&highlight=85.255.115.221)
How can I find out, if my computer picked up malicious software?
I have Avast running which didn't notice anything but that means nothing of course.
All threads mentioning 85.255.115.221 speak only of IE being attacked, but the popup (my FF is configured to prevent popups!) seems to indicate that they might have come up with something for FF2-users.

 

Hi,

you have got probably Win32/DNSChanger. Use this cleaner in safe mode => hxxp://download.bleepingcomputer.com/lonny/Fixwareout.exe

After it, you must check your HijackThis log.

 

Thanks for your help, I ran hijackthis but the logs were clean
(no suspicous software, nameserver in the tcp-ip settings was not redirected, no malicous hosts entries).
So I assume, that google actually presents redirected pages.
I excluded ukrainia from my router, so I hope, this was the last thing I heard from 85.255.112.0/20.

 

What if you downloaded something that, as part of its abilities, was hiding itself where you have been looking and removing its presence from any (HJT, etc) logs?