I have Ubuntu 12.04 desktop running on my box. I enabled 'auto login' for my account (only account on system) and it has worked just fine before. I usually have it as a headless server. I needed to use the desktop for something but it won't let me login. I can SSH to it, use the Transmission Web GUI, webserver and everything else, except at the login screen. When I enter the password, it acts like it's logging in but then comes right back to the login screen.
I tried creating another user and using the auto login for that user and it works fine.