well....its very complicated...
the REAL problem is the A64 Mem controllers...the max that they officially can run at is 333Mhz, NOT 400...however, most of the time they can.
for some reason, on some motherboards, they have more problems then others, not sure exactly why...
however, i've found that BIOS flashes do help some...
when i recieved my board back from RA the first time, i plugged eveything in, etc and booted up...BSOD, and i couldn't understand why...
the BIOS was F3 (i think), all i needed to do was update the BIOS tom F4, and it worked like it did beforehand...
have you tried enabling 'T2 Timings' that may help...