hello, please start firefox in safemode (by pressing the shift-key while it is launching) & go to firefox > options > advanced > general & disable hardware acceleration.

I don't know what systems people are suggesting doing shift-launch on, but it doesn't work on my XP system or the 7 system that I was trying to fix. Ctrl-Launch still just results in a crash. No 'safemode' option that I can see or get an option for.

At any rate, I 'fixed' the issue by installing one of the x64 (nightly) builds, but it had been running the non 64 bit version previously and I can't figure out why it stopped. I guess I also kinda don't care either though.

as an alternative you can also launch firefox into safemode by going to the windows start menu > run (or press windows-key + R to bring up the run dialog) & open: firefox.exe -safe-mode.

the problem likely started with installing windows update KB2670838, which has caused some instability issues on systems with certain graphic chipsets: http://support.microsoft.com/kb/2670838