Does anyone have any issues when trying to use 4 1GB memory modules ?

I am having issues where the motherboard will just not post at all, I have tried using differenct bios, different volts and timings but nothing works.
But when I only use 2 of the modules I have no issues at all.

I have also tested the memory modules (2 at a time) with memtest with no problems.

I have OCZ Reaper 8500's


Cheers
Wally