I cannot, for the life of me, figure this out. I cannot be the only person who is attempting this setup. Essentially, I have a Radeon 5850 and 2 22in monitors connected DVI to DVI and now i have a TV that I want to connect. Initially i tried the whole HDMI + 2 DVI which obviously didnt work and i gathered that it was to do with one display having to be on the DisplayPort. So i got myself a DisplayPort to HDMI adapter and still i cannot get it to run all 3 monitors. It automatically disables 1 of the displays when i plug in the DisplayPort section.
Funny enough, you are NOT the only person with this issue . I'm in the exact same boat. I'm using two 24-inch monitors connected via DVI and a third display, my 46-inch LCD, connected via HDMI. I asked XFX for advice, and they came back with an answer. See my notes on the support ticket here:
One 24-inch monitor to be connected via either DVI
One 24-inch monitor to be connected via DVI through the Mini Displayport using an ACTIVE Mini Displayport to DVI adapter
One 46-inch monitor to be connected via HDMI
It's important to note that Mini Displayport adapter be an ACTIVE adapter