this will be a strange report, because i can't debug properly.
starts...but crashes when i access some ssl pages or flash pages (not all)
it's using mozilla-launcher script.
100% reproduceble here, always same problem with google adsense ssl page.
i'm using a bookmark page, so it's not input related or similar.
i don't know what that script does, but it's weird.
i tried to start via gdb, but it fails, obviously, it's not a binary.
Which version? Emerge --info missing as well.
after hard investigation i just found tha mplayerplug-in breaks firefox.
now i'm testing heavly and seems really stable.