first check that the mb bios is up to date and there no patches for ram. asus tech said this on a forum and is smart..you cant tell if it a dimm or aa bad ram slot till you run memtest on one stick of ram that known good then move that stick to a slot you think is having an issues. if it passes then add another dimm. have that one change to one of the slots. if the slots look fine then check the new ram and old ram with cpu-z to see what the spd info is of both rams. sometimes with mb the voltage or timing needs to be changed or set to xmp mode. if the ram is fine it could be that one ram stick is 1/2 the side of the other. on your mb they may have to be two match sets of ram.