Ubuntu 12.10 stucks in a Login Loop

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http://askubuntu.com – My problem: As you can guess my Ubuntu 12.10 stucks in a login loop when trying to enter my desktop. Means the screen gets black and soon after that the login screen comes back. I'm a Ubuntu Newbie so if there's any answer please explain in a simply understandable language. I've already read that the problem might be caused by an error depending on the graphics, so I post my graphics to: My graphics: ATI Radeon 7670M (HowTos)