To the op...you used the bios flashback tool and did the bios updates and the efi bios says the right number in the bios?? if it does try this. if he using an aftermarket heat sink make sure it not overtight on the cpu. check under the cpu for bent pins.
you can try some other ram and see if it the ram or mb. myself I go a mb that works fine with two dimms but locks up with three.
as it been rock soilid with two dimms i did not pull it and send it back to asus for replacement. sounds like you got a bumb board.