Okay I know this is probably going to be difficult to answer so I'm hoping somebody as seen this. I'm running Fedora 16 64-bit using KDE. Firefox 11 and 12 crash frequently, about every minute to two minutes. Even if I'm not using it and it's just open, it crashes. I uninstalled it and deleted all profile data for it, reinstalled, and it still does it.
My OP is here: http://ubuntuforums.org/showthread.php?t=2051275
I found nothing in my Firefox setting that would cause it to crash and I never got a crash report from Firefox to send. During the time all these crashes/freezes occurred I was running the Cinnamon Desktop. I went back to Unity and everything runs smooth.