I have a AMD FirePro V4900 graphics card with two monitors plugged into the display ports and one monitor plugged into the DPI port. I can only get two monitors to work at one time, either the two that are plugged into the display ports or one display port and the DPI port. Can someone help me in getting me directions on why I only have two monitors. The system shows that I have three plugged in but one display shows it disabled. Help please!