I hope I'm not thread jacking here, I have a very similiar problem.
The system:
Silverstone SG06-450
H55n-usb-3(rev-1)
Intel i7 870
MSI radon 6870 Twin Frozr
Patriot PSD38G1333K 8gb dual channel (currently)
Windows 7-64bit
The Problem:
Built the system (using Corsair CMX8GX3M2A1333C9 8gb dual channel) and it worked great for about two weeks. Then in the middle of WoW (the system's primary use) I get a black screen with a small box slowly bouncing around the screen say something like "not optimal resolution 1900x1200" or something very close. Total lock up, so I powered off. On restart, it won't even get as far as the bios or boot sequence. The three (green/yellow/red) LED's on the mobo light up and stay lit, and after about 5-10 seconds the case power indicator begins to flash. No boot, can't boot from DVD, nada. RMA'd the mobo, and upon rebuilding the system, I got a brief flash of the Gigabyte poster (it looked like the box art) and then back to no boot, solid LED's, flashing case light. Thought maybe it wasn't seeing a HDD, replaced it, no change. Someone suggested defective memory, so I put one stick only in slot one, got one boot, shut it down normally to swap cables and then when powered up, back to no boot black screen. Exchanged the memory for the Patriot and system booted up fine into safe mode, so I rebooted into regular windows and it worked great for about five minutes, then back to same black screen, same bouncing message. Nothing is hot, nothing smells like burnt electronics, all fans are powering up, it seems the graphics card is outputting when it gets a boot...
Any chance it's still a memory compatibility issue and I should change to non-dual channel? Everything seems to be getting power, so I don't suspect the PSU, but...?
Thanks for your time,
-M