We have a similar config, since I also use 667 DDR2 (Crucial Rendition) but it's forced to run at 800 (upped voltage from 1.8 > 1.9) with my CPU set at 200 X 16 = 3.2ghz (@1.4375volts). My ram divider is set to 800mhz or CPU/8 in my bios. These are the lowest possible voltages I run passing...