I can not verify your question about the BIOS,, I was using the BIOS when my system would not go into X, and after I upgraded my BIOS to 5-22-03 my X started working but I believe it was because of the other changes I made to my system and nothing to do with the BIOS,, I will be able to verify this on my other system when I have time since it also uses the EPOX 8RDA+ board along side an NVIDIA graphics card.. I have Gentoo on it now and ran into the same problem with X as I did on my current system,, my BIOS on that machine is still 3-22-03.. So I will not flash BIOS and just make the same changes.. ONE thing to note is that nvidia just released support for AGPGART drivers on there website which are better performance.. It gives you the chance to compile in the kernel now agpgart for nvidia chipset.. But my machine never had any problems locking up or acting funny until I tried to startx,, then it would lock up or garbled ascii text.. So your problem may be different. Nonetheless just remove dri-rendering from kernel in char devices and install nvidia latest nforce release and compile agpgart for nvidia chipset into kernel.
thankyou and good day. Im not proof reading this so take it as is.