I have a Radeon 6970 video card that says it can support up to 2560 x 1600 resolution on up to 6 displays. I just bought a Dell 30' U3011 monitor and I cannot get the Catalyst Display Manager to slide above 1920 x 1080. I updated all my drivers. I am using the provided dual link DVI cable that came with the monitor. What else do I need to do?