P5LD2 Deluxe-auto reboot

I managed to get my 930 running at 266fsb with 1.375V. I ran Memtest in BIOS and no prob. I have a pair of DDR2 RAM at 1.9V. The problem is when I try to run 2 instances of Orthos(Large and small fft) and ATI tool or the Jap HDR testing program my PC automatically reboots randomly. And the funny thing is this happens only when I switched of my LCD. Orthos is perfectly stable. No artifacts either on my 7600GS(running at default clocks).