I have this same issue, but it might have been taken care of by swapping my 10 year old Packard Bell PS/2 keyboard with a newer E-machines PS/2 keyboard I had laying around. I got the idea thanks to this forum. I've been trying to get my PC to crash since Saturday, October 22nd with the new keyboard, and it hasn't crashed as of yet. My specs are down below.
Also, my problem has just started about 3-4 weeks ago.
This is what I have done so far to troubleshoot the problem:
*Swapping my Antec 350 Watt PSU for another of the same PSU units
*Updated all drivers and updated bios to 1.9
*Swapped my Kingston Value 3200 dual DDR 2x512MB sticks with Corsair Value 3200 dual DDR 2x512MB sticks
*Read the XFXforce forums
*Tested the temperatures of my CPU and graphics card by running in a window (CPU never rose above 50C and the graphics temps were in normal operating range)
*Checked the system for any IRQ conflicts
*Bought a new RaidMax 450W PSU on a 14A 12V Rail
*Swapped the XFX GeForce 6800GT PCI-E video card with an ATI 9200SE PCI video card (this worked fine for about 4-7 days then the same problem occured)
*RMA'd my XFX 6800GT card (I thought my ATI card worked fine)
*Swapped my Packard Bell PS/2 keyboard with a E-machine PS/2 keyboard (This seems to have fixed the issue)
I've read on these forums that another person had the same problem. He claims that he swapped his keyboard out, and it appeared to fix the problem for him. My computer also has been working fine since the swap; however, it hasn't been that long, and the power loss happens randomly and not as often with my ATI graphics card installed (I already RMA'd my XFX 6800GT appearantly for no reason now
). So, I'll let you know how things are going. My PC has been running problem free so far for three gaming sessions of about 1 hour each. I'll let you know if I find anything else out about this problem and keep you informed of my testing.