2 months ago I installed Ubuntu 14.04., but today the Update manager showed me some recommended updates, one of these upgrade to 14.04.1 LTS. After installations the pc restarted, but cannot run Ubuntu GUI. Only show the command line black screen and ask me my login and password. I do not know what to do to fix this problem, I tried to reinstall nvidia drivers, but it did not work. Thanks for your time and support.