Asrock AOD790GX Cold Boot problem with Phenom II 720

My system powers on from a cold boot with with no signal to the monitor or hard drive usage when I turn ACC on in the bios (to enable the 4x cores). Temporary solution to get system on with 4 cores is a simple restart after the cold boot. I've read a few forums and some people are getting similar problems yet no one has found a viable permanent solution. General consensus so far point to the motherboard with a possible future bios update from the manufacturer but I've yet to receive any support from Asrock (or rather, any body so far). Any ideas, solution or similar experience?

CPU: Phenom II 720x3. 0904EPMW. 4x cores stable @ 3.5ghz 1.45v with back to back 4HR total test using OCCT and Prime95.
MOBO: AOD790GX/128MB. Bios 1.4 (current).
VIDEO: Radeon 4850
MEMORY: G.Skill PC6400

And yes, everything runs fine with ACC off (with the exception of losing the 4th core). I could manage restarting the computer once after every cold boot but a part of me doesn't feel right.

Thanks all!

UPDATE: Board has been RMA'd. One thing going for Asrock is their super fast RMA process. Replacement board in hand after only a week. Very impressed.

Same symptom as before but now system hangs at startup even after a reset with ACC off. Asrock tech support suggest to RMA as CPU worked fine when I switched it to another motherboard.