How many users have you got defined? Just one? Have you tried any other user?
It sounds like you may have some bad data stored for the user you are logging in as.
If you have only one user, try logging in as root. If that works, then we know it is not the desktop code; KDE Xfce etc. If that fails, then it may be the desktop that's borked. If this is the case, you can remove the desktop on the command line, and re-install just the desktop.
What desktop did you install? Another option is to install another desktop, and see if that will load.