Go to BIOS setup and load setup defaults then set the memory frequency at DDR667 and set the memory Voltage to 2.0 Volts and increase the NB or NB/MCH +.2 Volts leave everything else at AUTO except Disable Legacy USB and then run www.memtest.org on the system.
Yes NB = North Bridge and the actual setting you want to change is the memory controller Voltage which can be called one of several things but usually with Intel Chipsets its called NB/MCH Voltage Memory Controller Hub