Thanks, Metadog. (Sorry to ask a bunch of silly questions, but saves a lot of guessing.)
Try the instructions here:
http://forums.mozillazine.org/viewtopic.php?f=38&t=1858685&p=9195115#p9195115
I’m sorry I don’t have more time to give more details, but I think that should set things right. (Please let us know either way, or if you run into any trouble.)
It appears to be a fake, hidden Firefox add-on, probably installed by the malware you already removed with Malwarebytes and Spybot S&D. Once you’ve manually removed it, it shouldn’t come back (unless you get infected again).
Malwarebytes and Spybot S&D will hopefully soon update their databases to include this. (As you probably know, one should always be sure to get database updates before running scans. Some malware blocks this, so one might have to scan multiple times.)
In the future, please also use Spybot’s “immunize” feature once a month or so—it’s very good at blocking browser exploits. When I have to use Windows, I also like to run SpywareBlaster
http://javacoolsoftware.com/spywareblaster.html
which provides similar, passive protection. (They work great together.)
If you’re really in the mood to install more software, grab the WOT (Web-of-Trust) Safe Browsing Tool Firefox add-on
https://addons.mozilla.org/en-US/firefox/addon/3456/
http://mywot.com/
which warns you before you visit many harmful sites, and SpywareGuard
http://javacoolsoftware.com/spywareguard.html
which augments SpywareBlaster with a (small) running process that actively blocks anything that still gets through. (Spybot’s immunization and SpywareBlaster, by contrast, work passively, without running any extra processes.)