Is the memory sticks you have single sided or double sided? Apparently that makes a difference with the 64 chips, with some mobos, if you have 2 sticks of double sided ram, since the ram speed controller is now a function of the cpu and no longer of the mobo/fsb, the ram speed will drop to 333 because the cpu cant handle 4 sides of 400. It sucks because that happened to me. One more thought, with some people, it helps to take your HT multiplier off auto and set it at x4, see if that works