I have 4 monitors, 3 are the same model and specs (Asus 21.5" connected via DVI). The fourth is an HDMI monitor connevcted via the HDMI port on a graphics card. I have 2 of the 21.5 monitors being driven by an EVGA GTX 580 nVidia card and the other two are driven by an EVGA GT 520 nVidia card. When I attempt to select the HDMI monitor for video output, the monitor isn't listed in the drop down for available desktop video monitors. In fact, only one monitor displays... the Asus 21.5 connected via DVI on the GT 520 card. The second monitor on the GTX580 card and the HDMI output don't show up.
Any thoughts as to why this is happening and how I can get them listed/usable?