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.
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