No screens found - only command line login showing up

I obviously destroyed my graphic settings by attempt to switch to Gnome after a KDE installation (Mageia 3 Beta 2) was running perfectly fine.
All I can get to now is a linux prompt to login.
If I login and type "KDE4" I get a huge Error message ending with "fatal server error. No screens found. (EE).
It must have a connection in a destroyed "xorg" configuration because by trying to switch to Gnome I saw, that it wasn't clearly visible/available. It was not shown as "Gnome" in the menue as "available" I first went to something like "randdrake?" and then to something like "ICEM" and finally ... the command line prompt only.
Any help available?
All I can get to now is a linux prompt to login.
If I login and type "KDE4" I get a huge Error message ending with "fatal server error. No screens found. (EE).
It must have a connection in a destroyed "xorg" configuration because by trying to switch to Gnome I saw, that it wasn't clearly visible/available. It was not shown as "Gnome" in the menue as "available" I first went to something like "randdrake?" and then to something like "ICEM" and finally ... the command line prompt only.

Any help available?