I put the memorystick that was in the third slot into the second and now it works on 400MHz with both sticks in it!

Guess the motherboard automatically puts the clockfrequency at 333MHz if a module is in either slot three or four or perhaps another stick is also needed to be in slot one or two as well (the latter is what I actually believe to be true).

The CMD-ADDR Timing Mode, this is what I meant in the first place, is still at 2T, but I think it should work on 1T now that the sticks are in slot one and two instead of one and three. Anyone who's more knowledgable care to fill me in whether this is true?