[ATI] Radeon 4870 Second DVI port not working

So I have recently built my first desktop computer and everything has been working relatively fine; however, I can't get one of the DVI ports on my Radeon 4870 to work.

When I first booted the system I received some strange post error, after searching the net I noticed an that it might have something to do with the graphics card. I reseated it and the computer posted without a problem. However, I did not get a monitor picture. I rebooted with the monitor in the other DVI port, and it worked. I have installed the OS and Drivers and everything is working fine except for that second DVI port. Windows 7 recognizes that there is a second port, but when I plug in a monitor, it does not recognize that a display is attached. There is no on-board graphics on my Mobo, and the Catylist CC that Radeon makes does not manage displays in windows 7 (according to their tech support).

My question is: What is the most likely cause? I suspect its the video card and its just faulty. Could it be the mobo even though everything else seems to be working perfectly? I appreciate your help!

Problem was resolved by replacing the graphics card. The system is working great now!!