Need help with reboots

[zod96]

I've got 4 GB's of PC12800 in my intel x48 chipset motherboard. Now when I turn the computer on it will start for a few seconds then turn off then turn back on and just sit their no screen. Yet I can hear and see all the fans working hd etc. I tested the ram and its fine. I checked the cpu and its fine and the HD as well. Now I've read that with the X48 chipset you can only have 2 sticks of PC12800 ram, I have 4. But it goes down to 10666 speeds since my CPU is only 1333FSB. When I took out 2 sticks and just left 2 in its fine. But I know the memory is good. The default vdimm for these sticks is 1.9. The intel bios shows them with SPD at 1.5 vdimm, could this be it, or could it be the PSU?