I have XP and something has been crashing my Firefox. I've tried
everything I can think of, I even ran it with no antivirus. Something
is STILL driving CPU Usage up to 100% for no apparent reason, cuasing
FF to crash. Any idea what it might be??

The FF Crash Reports usually say Exception Violation which means
something wrote to the memory where it shouldn't have.

I have no firewall either. I tried reinstalling FF and Flash too.