Motherboard issues? ASUS P5B - Deluxe

[civic00typer]

Maybe a motherboard issue here... I just wanted to get some opinions before I start trail and error troubleshooting. My media center consists of 12HD's, Asus P5B Deluxe, Core 2 E6300, Crucial Ballistix 2GB Kit (DDR2-800), Enermax Liberty 620-watt PSU, and a Highpoint RAID controller. After a week or so of up-time the computer starts to have memory issues. Windows will blue-screen, and these memory issues have been verified by Memtest86. Once the computer is powered off it will not POST again. I cleared the BIOS, unplugged the MOBO, removed the battery, and removed the CPU. Typically I end up letting the computer sit there disassembled because I have very little time in my schedule for troubleshooting. When I get attempt to power the computer up after some downtime it will POST and have no memory issues. I actually took the RAM and put it in my other Core2 rig and tested it for 30+ hours with Memtest86, no errors found. I then proceeded to test the power supply. I used a power supply tester, and use the 24-pin, and the 8-pin aux plug. When I have anything else plugged into the power supply while using the tester, it will cycle on and off making a clicking noise. Is this typical? I can't decide where to start... either the motherboard or the PSU. I hate intermittent problems.