[xubuntu] no login menu after xubuntu starts

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http://ubuntuforums.org – I'm running Xubuntu 12.04 64 bit edition. When I start up my computer the xubuntu splash screen shows up and then it goes into command line mode. I can still login by typing my username and password but I have to type startx to start up xfce. This does not happen all the time. How do I fix this? (Hardware)