HTPC won't post with HDMI cable plugged in

[ZipSpeed]

I'm fresh out of ideas on how I can combat this problem so I'd see if I can pick anyone else's brain.

The computer won't post with the HDMI cable plugged in. In order to get the computer to boot, I have to unplug the cable first, let Windows load and then plug the cable back in. This problem doesn't appear when I say attach a DVI cable to my computer monitor.

Specs:
CPU - Intel e5200
Mobo - Intel dg31pr
Video card - Gigabyte 4670

Mobo has the latest BIOS. Tried messing around with a few BIOS settings to no avail.

Any insight would be great. Thanks.

 

[Schmide]

Maybe the graphics card sound drivers hanging during boot?

What OS?

 

[ZipSpeed]

Will try disabling onboard sound when I get home.

Windows 7 64-bit. Latest Cat drivers.

Thanks.