Linux Mint Login Help

[rehrnsberger]

Hello Im new here. I have a pc I installed Linux Mint 12 on it last week. I have been using it no problem. I updated the files through the update manager. When it was finished I rebooted the computer. Apon reboot the pc stops at a login screen that I never had seen before cause it autologged in. I try to log in and it starts to load by the screen changing black, then just pops right back to the login screen. I does not matter how many times I try it. I can log in a root and change the user password, I have, and it still does the same thing. As I said it will log in as root. Any ideas???

I know the password and user name is correct.