You can own 2 single sticks of ram that individually are okay, they will pass mem test no problem. However combined they will hate eachothers gutts. Have you tried swapping ram, like originally it was in Dimm 1 and 2, so swap Dimm 2 with 1.
Your ram simply hate each other.
i have tried the ram in all combinations of the slots, at present i have them in slots A2/B2 as recommended by the motherboard manual.
So what you are saying is that i may need to RMA the ram?