The great abit IC-7 + 2x corsair cmx256 3200C2PT mystery, PI wanted!

Today I received 2x Corsair XMS cmx 256-3200C2PT v3.1's I installed them on my PC (p4-2.4 800mhz FSB +Abit IC-7 i875) in dual channel mode. My PC starts but while booting it simply doesn't do anything (think you could call it a pc crash), after some restarts i do manage to get in the bios but also there it simply stops doing anything. I also tested them 1 by 1 in single channel mode. This resulted that my PC could boot without any trouble, the only problem was that windows refused to start and gave blue screens. Another strange thing is that when i entered the BIOS it noted that the timings set by the SPD were 3-3-3-8 instead of 2-3-3-6. when I manually put it on 2-3-3-6 and restarted my PC it didn't even start and kept beeping. Afterwards I plugged in my old memory beside it (4x 256), this time my pc booted and started windows without any sort of trouble (timings 2.5-3-3-7). I also ran memtest86 v1.20 and it didn't find a single error. so next to my old memory it works like a charm. After that i removed my old memory and tried again to run it again like before (hoping it would now run without trouble this time). It didn't the same problems all over again... I really don't understand, the memory appears to be fine according to memtest, but why doesn't it want to work ? :(