ORIGINAL: JB COMP
I did full scans with AVG, Spybot and Ad-aware and none of them found anything.
FF still jumps around in memory usage from 170mb to 250mb (with out me opening or closing any tabs.)
No offense but AVG, Spybot and Ad-aware aren't the best for securing and scanning you computer. For a real time anti-virus I would choose Avast or Avira free over AVG. For free anti-malware/spyware scanners I would recommend MalwareBytes, SuperAntiSpyware and A-Squared.
I also recommend visiting Secunia's site to do an online scan for vulnerable programs you may be running. They have an online scan or a downloadable version you can use. It will let you know if Windows, Flash Player, Java, Media players, etc are up to date. Here is the link.
http://secunia.com/vulnerability_scanning/
As far as Firefox's memory usage, did you look at the first link in post #17?