Ok I just tried switching things back around and for some reason neither chip will allow POST on the first board but both will come up with the same BIOS checksum error on the second board....
That's sorta what I was suspecting. BIOSes generally don't just get corrupted at random... it's usually a result of a failed attempt at flashing. Since both chips work in the other board, it's not a corrupted BIOS ROM. Sounds like you have something else wrong with that one board. I'd check it over carefully, looking for physical damage... broken components, damaged traces, corrosion in chip sockets, stuff like that.
For future reference, though, on the matter of awdflash.exe, it's not a board-specific utility, so you can get it elsewhere. Older boards often tend to need older versions of it, so it would probably be worthwhile to keep a few different versions handy. Alternately, Uniflash will work for most boards.