LinuxQuestions.org - gdm trouble

I screwed up a bit, and need to do some changes in the gdm-config files (those that contain whicht session I am enabled to start)
Whichever session I choose to start just tells me that there is no desktop. Only one I can run is safe terminal mode (KDE and xfce are screwed up). I can start kde from the safe terminal though, with startkde.
Think there could be some problem with th /etc/X11/xdm/Xsession/-folder which is empty.

Anyone who can help me?
It failed after a electrical-shortage in the neighburhood, in the middle of installing a gdm-update. (tried installing the update again after, does not work)

It doesn't get the log of the messege for some reason, debug won't either
in the en of the messege it says, can't execute child ***** /etc/X11/xdm/Xsession startkde

Tnx in advance to whoever can help me :)