lightdm - Ubuntu gets stuck in a login loop

My Ubuntu is stuck in a login loop when trying to enter my desktop. When I login, the screen gets black and soon after that the login screen comes back.

I've read that the problem might be caused by an error depending on the graphics, here's my graphics card: ATI Radeon 7670M

Did you end up here after running sudo startx? Nevertheless:

Press Ctrl+Alt+F3 and login into the shell.

Now run ls -lA. If you see the line

-rw-------  1 root root   53 Nov 29 10:19 .Xauthority

then you need to do chown username:username .Xauthority and try logging in (you may also need to do the same for for .ICEauthority).

Else, do ls -ld /tmp. Check for the first 10 letters in the left: they should read exactly so: drwxrwxrwt.

drwxrwxrwt 15 root root 4096 Nov 30 04:17 /tmp

Else, you need to do sudo chmod a+wt /tmp and check again.

If not both, I'd recommend you either

1. sudo dpkg-reconfigure lightdm


2. or uninstall, reinstall it.

Now press Alt+→ until you reach the login screen again, and restart.