well, does re-flash the BIOS to the original BIOS, does boot the system?
regarding the Nvidia's Linux driver and Epox 8RDA+, i'm afraid there's no other workaround at this time, since u can only :
1. downgrade the BIOS (not working for u)
2. wait till Epox release new BIOS (hopefully fix the prob)
3. wait till Nvidia release new driver (also hopefully fixed the prob)
4. forget Nividia driver, use nv instead (say good bye to 3D in Linux