Are you able to get into the Ubuntu log in GUI mode? That would be the splash
screen? If so log in at open up the terminal at Applications>Accesories>Terminal
The terminal will open up and type in
sudo dpkg --configure -q
Some thing did not install right or some thing did not down load when
installing.
it will ask for a password. It should be the password you selected to log in
and run as root

If you only get
$username
You can type the same above and see if it corrects it.