Originally Posted by Deanjo
Don't drain the BIOS to reset it, just get into it and there is an option to reset to factory "optimized" defaults. That is all that should be needed (assuming you are running the 0901 BIOS). I have the exact same board with a GTX-580 and the exact same issue (which is also present in a M5A97 EVO with a GT 520 as well).
I forgot to mention that "optimized defaults" was the first thing I tried and yes the BIOS is 0901. Draining the BIOS was the last thing I tried.
"optimized defaults" was the one that came up without USB and network but didn't boot into X.
One other funny is the USB keyboard works in the BIOS but on boot it doesn't work so anything in grub can be changed - adding options or selecting images to boot or any keyboard operation. When it boots console login and all other stuff works.
I have also logged a support request with Asus as the motherboard and the video card are theirs.