Are you using the hdmi and dvi or two dvi ports? I am running 3 monitors out of my radeon 6700 but had to use 1 dvi 1 hdmi and the intel graphics port . When this happened to me it was all software driver related and was eventually resolved by deleting the driver …rebooting the computer and then re-installing the drivers for setup. The " identify monitors" button in control panel gave me a slight clue as to which was which when setting the resolution again. They do not seem to be recognized for what they are by windows but they did set up properly with a little tweaking