Fix for can’t start graphical apps as admin.

Earlier today I would get an error about not being able to read the users Xsession file or something when I tried to start any Administrator program from the menu. sudo worked fine, but gksudo (the graphical password entry thing) didn’t.
Solution: full root partition.
Tips to free up space:

Restart. This clears /tmp
sudo apt-get autoremove && sudo [...]