Re: Externally flashing non-working GTX280
This will be tough to diagnose on your own. Do you have any reason to believe that the bios chip is screwed? Do you have any reason to believe there is any physical damage?
Is your bios/flash chip removable? If not, I don't see how you're going to give it a reflash without some seriously careful soldering.
Otherwise, have you performed a visual inspection of the board for broken components, leaking capacitors, burned components or cold solder joints?