Just finished upgrading from Ubuntu 13.04 to 13.10. Everything works fine. After the installations, I restart to finish the installations. In the log in screen, I put my password and then it goes back to the log in screen. I've tried so many times, still the same.
Note: Using Unity, running 13.04 before using MacBook Air with single OS.
I had the exact same issue after upgrading from 13.04 to 13.10.
None of the solutions here worked for me, so I found this bugreport. I removed Cinnamon/Nemo with
sudo apt-get remove --purge cinnamon*and
sudo apt-get autoremoveand now everything works fine.