It sounds like there is a problem with your X configuration.
I guess you should see things again when you hold Ctrl+Alt+F5 simultaniously.
Log in, and try running this command:
sudo dpkg-reconfigure xserver-xorg
disclaimer: I don't use ubuntu, I just googled this page: http://www.cyberciti.biz/faq/ubuntu-...m-xorg-server/
I have no idea if it will work