put the stock GC bios or try on 3-4 cards ?
I lost original bios so can not try it, tryed on 3 cards - the same crash
-There are databases with original BIOS on many sites.
-You can just undo settings what you did on BIOS and that would be your original. Unless you did not do changes yourself? In that case you cannot trust BIOS and that must be the first step before any further troubleshooting.