Originally Posted by Yellowbeard
Try leaving the timings at 5,5,5,15 for now and increase the voltage to 2.1v. Then, try changing only 1 timing and booting to Memtest (
www.memtest.org ) for 1 full pass. It may be a chipset issue with a single timing. So far the P5KC MOBOs are not OCing well but, you'd think this system would run DDR2-800 at 4,4,4,12. If it won't you may want to RMA.
As Yellowbeard says. My problem was a faulty MB. I put the memory into my new P5QD, upped the memory to 2.1v, set the speed to 800 and timings to 4,4,4,12 and off it went without any hastle at all.