[ubuntu] Won't boot after installing proprietary video drivers

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http://ubuntuforums.org – My computer has an AMD Radeon HD6890 graphics card, and when Precise was running I had installed the proprietary drivers from AMD's website. After I updated to Quantal, Ubuntu would not detect my monitor's correct resolution, among other things. I went back on AMD's website to see if there were updated drivers and found some. Then I uninstalled the old drivers (which seemed to fix the resolution issue, but prevented Unity from running properly since the dock was no longer displayed). I installed the new drivers, following the instructions on this page: http://wiki.cchtml.com/index.php/Ubuntu. (Hardware)