Similar experience with my Sawtooth running a 1.2GHz PLX CPU. In my case the DIP switches which set the buss multiplier evidently glitched and it went to 1.6GHz, which is way overclocked for a 1GHz 7455 (PowerLogix had already overclocked it by 200MHz). It overheated and the symptoms were the same - memory errors, buss errors, and just generally flaky. I'm surprised it worked at all at that speed, but it did work apparently for a week or so before it finally kicked the bucket. I had noticed the fan was running at high speed a lot, but didn't think to investigate until it started crashing. It's possible of course that the bad part is a cache RAM chip instead of the G4.