14.04 unity does not start after login screen

In Ubuntu 14.04, after arriving at the lightdm login screen and entering my password, the screen briefly disappears, but then comes back to the login screen. When going to terminal with ALT-CTR-F1 and doing sudo startx I get into X but no top and side bar.

With sudo startx unity I see the side bar but no status bar. And the screen looks weird and does not work well.

I did not change anything to my configuration, I guess it has been some automatic update.

Any suggestion as to how to solve this? I really do not want to reinstall.

I had a similar error and the problem was due to my /tmp/ directory having the incorrect permissions and .Xauthority. This Answer worked for me (I copied and pasted it in case it gets removed, @SiddharthaRT is the original author):

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

Now run ls -lah. If in the output 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.

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

dpkg-reconfigure lightdm

or uninstall, reinstall it.

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