My system reboots. HELP

[m@d-m@x]

I have a big problem. My system randomly reboots.
The story starts with i bought a new system 4 months ago.
Asus P5K premium motherboard
Intel Q6600
2x1GB corsair PC6400
and more.
A few days ago i bought another 2x1GB ram (same as the others) but now my system randomly reboots when in windows. And it also reboots if i remove the new RAM, meaning its like the old system. I did some heat probing and nothing is wrong there and i also returned to normal speeds (no overclocking) still no solution. But i can run a memtest from dos in more than 24 hours just fine. I can also run a series of superPI no problem at all but it can reboot doing nothing in windows at other times. I can also play games for a long time and nothing happens but it can still reboot randomly. I have tried reinstalling windows 3 times with no luck so now im out of ideas so please help me.

[Leeghoofd]

Test each dimm with OCCT ram test, memtest ran fine here too for 10 passes, but yet had same issues as you, BSOD randomly, reboot,...
OCCT crashed with one dimm after only 12 mins, others dimms survived 2 hours of custom test... RMA'd the ram all is fine now...

Prolly one dimm that's dying..., you verified all the voltage settings and co ?

[m@d-m@x]

I think (only think :) i figured it out. When installing only 1 module in slot 1 (tried 6 different modules) i even have problems getting into windows before it reboots.
Right now i have 2 modules in slot 2 and 4 and with OCCT running in the background for about 15 minuttes now and no reboots.
Seems to me the mobo's slot 1 is broken so i guess ill RMA the board. Can anyone recommend a replacement mobo? i dont think the store has anymore of these boards and im pretty sure they cant fix the board :P