Graphical login fails for admin user... (Lubuntu)

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http://ubuntuforums.org – Hi, I just installed Lubuntu on my netbook. Now I can't use the graphical login anymore - after I enter my password, the screen flickers as if LXDE was starting, but then I get dropped back to the login screen without any error message. Where would I go looking to find out what went wrong? There must be some place where errors that cause this are reported, right? (Hardware)