Boot problem with 6870

[Lethargy]

I recently built a new computer. Here are my components:
PSU: Tagan TG800-BZ
MB: Asus p6T Deluxe V2
CPU: Intel core i7 950 clocked to 4GHz
HDD: OCZ revodrive 120gb and samsung spinpoint 2tb
RAM: Corsair XMS3 3x2GB DDR3 1600MHz
GPU: ASUS EAH6870 1GB DDR5 (radeon hd 6870)
OS: windows 7 64-bit

I am only able to boot my computer if I physically disconnect my GPU from the PCIe socket. Sometimes if I play graphics intensive games like crysis I will get a blue screen and I will be able to reboot. If I restart my computer before entering windows I will be unable to boot unless I physically disconnect it again.

The GPU is moderately clocked in CCC Default values are 915MHz GPU and 1050 MHz for memory. Clocked to 975 and 1100 respectively.

I have updated to the most recent version of my bios and drivers.

What is it possible to do in this situation?

 

[Nokiacrazi]

Maybe a hardware incompatibility?

I really have no idea...Wait for the experts!

 

[Mussels]

at this stage i only have guesses, my two would be some kind of weird incompatibility (update the motherboards BIOS) or maybe some kind of PSU issue - while it should be good enough, maybe the rail feeding power to the PCI-E connector on the card is failing and it needs a warmup to work?

 

[NdMk2o1o]

Do you have issues when the GPU is stock?

 

[Swamp Monster]

Have you tried switching to Turbo mode on your Power supply? If 12v rail you are using for GPU power, is bad, then this could fix that problem, because this switches multi-rail to single-rail.

 

[ocgmj]

I ran into the same problem recently. Turned out to be a bad PSU.