I am a running a Powermac G5 dual 1.8 with the latest OS X, and I cannot run Firefox at all, it asks if I want it to be the default browser, and then it freezes, every time, I have to force quit. I have tried deleting firefox, reinstalling it, and I've had no luck. (I've also tried the usual, rebooting, relogging, etc.)
A fairly thorough search through google has left me clueless still....