I ran across this post on one of the cigar forums I frequent. And it's an important point to see that FF 3.0.4 is affected by this (importance of upgrading in this case). I think many users have forgotten that safe-mode can make detecting and destroying virus/malware a lot faster. (the ol' KISS principle).

Anyways, if your FF isn't up to date, this might be good enough reason to.

..this one got into my computer through Firefox and really went to town. It was the "Gadcom" trojan and Google is all over it, if you're interested. It's a nasty one; it shut off my Windows update, the Windows firewall, and Windows monitor of my virus scanner. Stopped the virus scanner from communicating with the web. Prevented me from installing "Hijack This". Wow…..a really pestilent one. It appears that Firefox 3.0.4 was vulnerable, and the new 3.0.5 is not. First step, if you're a FF user is to get that upgrade.

The surprising news is that after trying a bunch of tools to get rid of it, Microsoft's new "Windows Defender" did the trick splendidly. Took a little finagling as the damn trojan wouldn't let Windows Defender update its signature files, but that's easy enough to do manually (instructions on the web page). Best part about this is that it's FREE for XP and Vista users. You can get it here:
Windows Defender

Even if you have a virus scanner (which I do), I can strongly recommend getting a hold of this and installing it. The price is right and it nailed the trojan, dead in its tracks and successfully cleaned it off my hard drive.