It's only running 8gb at a time. Runs fine with a 4gb stick in the a1 and b1 slots and fine with a 4gb stick in the a2 and b2 slots. but when I fill them all up windows wont run and it sends me to windows recovery which just stalls and does nothing. I've tested all 4 sticks and know they are good . any ideas ?? (cpu is a phenom II x4 840)