After I upgrades from 10.04 to 12.04 I cannot login to my main users account. Before the upgrade I had created another administrative user but had never used that account with the gui. That other user has no problems logging in. Guest, which I never used before this problem, can login without a problem. Only the main user has the problem.
At first the Xauthority file was owned by root, so it would just return to the lightdm login screen. But after researching that problem I removed that file.
Now when I enter the main user's password the gui seems to load a little. The mouse appears but all I get is a terminal, without any boarder, in the upper left corner. Only when I move the mouse into that upper left corner can I type commands. Any command works fine. When I type exit it returns to the lightdm login screen.
I tried comparing the /var/log/Xorg.0.log file after logging in with the alternate admin account and the main account but it every line starts with a different number.
The .xsession-error file had no additional help.