So I'm reviving this thread since I was never able to fix the problem.
I looked into RMA'ing the motherboard but for some reason the serial number isn't recognized by Gigabyte's RMA service website.
CPU and memory benchmarks work fine and all pass using an older XFX GT 240; it's just the 3D accelerated stuff that fails.
Installing the Nvidia forceware drivers causes a blue screen when it tries to enable acceleration. Ubuntu (and lubuntu) fail to start up due to the 3D...