Thanks, but no luck this time either. I used awdflash /tiny /Wb.
The first 1/2 of the first line was "No change" and the rest was all OK. Previous flashes were all white (i.e. no "no change" parts).
Still, same ol' code. I'm guessing it's not the BIOS after all.
Edit: OK, I got a new mobo on the way. I gotta say I'm almost completely sure this one's dead after all this testing and troubleshooting, but even if it's not, I'm not going to throw it out the window, so *if* it works it might come in handy in the future.