[ubuntu] No desktop wallpaper after login, frozen login screen instead

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http://ubuntuforums.org – After logging in with 13.04 the Unity side bar appears and I can interact with my computer fine. However, my desktop wallpaper never appears, and I am left with the frozen login screen in place of my wallpaper. I cannot right click on my desktop to open the usual context menu that appears there. Trying to change my wallpaper in Appearance Settings doesn't seem to help. Any ideas? (Hardware)