Comment 1 for bug 351293

Thanks for reporting this issue. Unfortunately, without some more information, there is very little can be done to resolve the issue. Can you use Ctrl+Alt+F2 to go to a TTY terminal console? You should be able to login, and run the updates again using "sudo apt-get update" and "sudo apt-get dist-upgrade". It is possible one or more items did not complete. After the updates finish, run "sudo -r shutdown" to restart the system.

You can also go to /var/log/ and copy the Xorg.0.log to attach to this report if the updates don't allow you to login again.