Another result, got it working perfectly at all stock volts and the ram underclocked. if your using a tower cooler, it hasn't got the heatsink fan blowing air over the north bridge heatsink and voltage regulator heatsinks. When I placed a spare old 80cm fan and even slowed it down untill it was inaudible over the rest of my system with my fan controller and had it blowing air from the ram area towards the northbridge cooler. Suddenly it overclocks allot more easily and stable too. take it away and it'll BSOD when you stress it.
So I think you need some airflow round the Northbridge. if your case is a wind tunnel it may be ok. If necessary add a quiet Northbrige fan too.