http://www.ubuntugeek.com/fix-for-cant-login-after-upgrading-from-ubuntu-13-04-to-ubuntu-13-10.html
I had the same problem and found a thread elsewhere that solved the problem in a different way.
As above, at the login screen use Cntrl+Alt+F1 to open a terminal window and login at the command line instead
by default you should be in your home directory,
use the command ‘pwd’ to show what directory you are in, in my case…
pwd
/home/peter
if you are not in your home directory change to it using
cd /home/’username’
here you need to remove two files (note the ‘.’ prefix on both) .Xauthority and .ICEauthority
to show the files type the commands
ls .Xauthority -hal
ls .ICEauthority -hal
Assuming they are there the command to remove them is…
rm .Xauthority .ICEauthority
then reboot the machine using
sudo shutdown -r now
After reboot I was able to login as normal
http://czmmiao.iteye.com/blog/1003810
chown $USER:$USER -R /home/$USER/
chmod 644 /home/$USER/.ICEauthority
