Well you may want to try reseting the bios completely with the little reset button on the back and redoing your bios settings to make sure something in the bios isn't causing the issue.
Also memtest86+ 2.11 proved to be reliable for quickly pointing out memory errors for me, test 5 was the one that would always error when I pushed my memory too far. http://www.memtest.org/
What are the voltages you are running?