[Graphics] Secondary Monitor not working

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http://www.kubuntuforums.net – I have 2 monitors, both are Dell UltraSharp U2312HM. I was previously using both as an extended desktop in Windows 7, and it was working great. Well, except the windows part... but that's another story. I am running kubuntu 13.04 64-bit, and my secondary monitor is not working at all. It is "on" but only black. I can switch the monitor cables in the graphics card (Sapphire Radeon 7870 Ghz edition) and both monitors can work as the primary, but I have no secondary still. I have gone into System Settings -> Display and Monitor and messed with every setting I can think of (moving (HowTos)