My Ubuntu Crashed, can't log into the system, what went wrong?

view story

http://askubuntu.com – I'm very new to Ubuntu. I did this : sudo apt-get -f install And when I rebooted the system, I couldn't log into the system. When I proceed with the user name and password I get a small pop-up saying : Failed to load session Gnome ( Log Out ) What went wrong? Are there any ways there to get back to my previous state? Thanks in advance. (HowTos)