I run 2 HD 5850 Black cards, the only way to get them to work is to use 3 diferent ports. 1 DVI, 1 HDMI, and 1 Displayport-anykind of conetion, Most common DP conection is DVI but you can find HDMI ones as well.
Must be an "Active DisplayPort" like this
http://www.ncix.com/products/?sku=55482&vpn=DP-SL%20DVI%20Adapter&manufacture=PowerColor The pacaging will usealy have that same logo on it some where letting you know its Eyefinity capable, also make sure your not getting the Mini Version as yours is like mine and its a standered DP. Link is to the one I bought years back.