I am running 12.10. Attempting to login via gdm lands me back at the login page. The behaviour is the same for when I switched to lightdm. Logging in with guest is fine, and logging in with a test account I created is fine.
If I access tty1, login with my account and then startx, I get to my desktop fine.
Any ideas? I have tried chowning Xauthority and then removing it but to no success. The problem appears to be a setting in my account, although I have no idea what as when I last used my computer before the problem occurred I didn't do anything abnormal (i.e. system updates or changing any user settings).
Solved thanks to help from Braiam. My ~/.xsession-errors.old file had the following:
/usr/sbin/lightdm-session: 34: /home/*username*/.profile: source: not found /usr/sbin/lightdm-session: 42: /home/*username*/.profile: Syntax error: "(" unexpected
I had recently added some lines to my .profile to provide useful git information in my prompt. It worked fine when logging in via tty1 and then running startx, however it seems it was stopping me from logging in via gdm / lightdm