Some mobos are set by default to read from the PCIE slot when a GPU is installed. This maybe the case for your mobo. You could either buy yourself a DVI cable, or an adapter, or simply remove the GPU to test this theory. If this proves unsuccessful, your mobo could be shorting. To eliminate shorts, breadboard your mobo.
For more troubleshooting tips, follow the link in my signature.
Thanks I figured this out just a minute ago but thanks anyway!