Actually, it doesn't...when i install the 433 ram it doesn't see it at all... and if i take out the 400 ram and just have the 433 in, then it refuses to even boot untill i take out the 433 and put the 400 back in...Are you using the xms3200 512mb 400mhz Corsair? That should work, it works on mine...

One further question... You say you have a dual unit...you are putting in pairs of chips, not just one right? Ya, i know, it's a silly question, but it has to be asked...duals require that you install ram in pairs... 1 in each bank...

Other than that, don't know what to tell ya, it works here...