[ubuntu] Log on screen reverts back to log on screen after entering password

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http://ubuntuforums.org – Ok..I'll explain what I did wrong, and then what I did to fix, which led me to my current dilemma. I thought I was going to be a smartypants and change my password to something really easy. Well, I goofed it up. When I tried to log on, I couldn't. So I accessed the root shell to change password, but encountered " change password authentication token manipulation error". I was able to get around that with "mount -o remount,rw /", and successfully changed the password. Now, the problem: When I enter the password on the log on screen, the screen goes black for a second, (Hardware)