I'm not really sure what happened.

All of a sudden, none of my applications wouldn't start. However, the only app I had open before I noticed this (Opera) still worked. I logged out and tried to log back in to see if that would solve the problem, and GNOME wouldn't start.

The loading window would pop-up, hang for a minute, and then crash back to the login screen.

I can still start KDE and my other desktops.

Can anyone tell me why this may have happened? And if at all possible, can somone tell me how to fix it?

Thanks.