Just some additional info, I ran firefox like:
$ strace -f -eopen firefox &> /tmp/ffox.log.txt
And here are the last few lines...
pid 6299] open("/usr/lib/xulrunner-1.9.1.3/res/
langGroups.properties", O_RDONLY) = 70
[pid 6299] open("~/.mozilla/firefox-3.5/t9hr4ll3.fbtest/extensions/
fir...@software.joehewitt.com/skin/classic/firebug16.png", O_RDONLY)
= 72
[pid 6299] --- SIGSEGV (Segmentation fault) @ 0 (0) ---
[pid 6299] --- SIGSEGV (Segmentation fault) @ 0 (0) ---
upeek: ptrace(PTRACE_PEEKUSER,6319,120,0): No such process
Process 6319 detached
[pid 6327] +++ killed by SIGSEGV +++
[pid 6326] +++ killed by SIGSEGV +++
[pid 6325] +++ killed by SIGSEGV +++
[pid 6324] +++ killed by SIGSEGV +++
[pid 6322] +++ killed by SIGSEGV +++
[pid 6321] +++ killed by SIGSEGV +++
[pid 6318] +++ killed by SIGSEGV +++
[pid 6314] +++ killed by SIGSEGV +++
[pid 6311] +++ killed by SIGSEGV +++
[pid 6310] +++ killed by SIGSEGV +++
No clue if that helps at all...