I think it seems you've tried anything I can think of. Not meaning to state the obvious but you do have the required .060 libs installed don't you? Have you tried booting with the key pressed that drops it back down to the 020 cpu?
What would be usefull is if you could log everything it does up to the crash to find out exactly what it's doing when it crashes, or even better something like snoopdos that duns during the bootup process, that'd help a lot in situations like this.
