I had the same problem with 3dmark05 rebooting. It only worked if it was unplugged.
I eventually convinced sager it wasn't a software or driver issue and they admited there is a "glitch" with the MB they are aware of. I just received my RMA and its working perfectly w/o any bad pixels.
Other then choppy dvd in the opening menu (resovled by turning off hardware decoding though a dvd proggy reinstall may fix it also) its all good.
Copy of my final email before they decided to RMA.
3dMark05 does successfully run and give a score.. without the power cable being plugged in. As soon as I try to run it with the power cable attached, it reboots or simply goes dark.
Installed Halo and FarCry... Both games loaded and were playable. Farcry had some texture and lighting problems that I couldn't resolve via settings. (incorrect interior lighting, washed out textures, water dosen't have the reflectivity it should) I tested it with low, medium, high and very high settings. Halo appeared to play w/o any issues.
Halo and Farcry are both DirectX games.
Lineage 2, BattleField Vietnam and Jedi Academy are openGL (the unreal engine I beleive). I tested them with and w/o the power cord plugged in.
Jedi Academy still errors out with the same error with and w/o the cord plugged in
Lineage 2 loads up and plays beautifully, without the power cord plugged in, It crashes soon after plugging it in. Still reboots when game is started with cord plugged in.
Battlefield seems to be running correctly following the successful 3dMark05 tests. It currently runs with the powercord plugged in.
I would say its a problem with openGL and the voltage. Cause it reboots trying to load an intensive openGL app.