Hello, all:
I have been running Lenny with the non-free nVidia drivers for a while now, but decided to run testing RC2.
When I was done my monitor had a solid blue-gray background and the mouse pointer, but none of the GUI parts displayed (blank).
After a couple of checks I went back to the gdm logon screen and opened 'sessions' to _not_ find Gnome as one of the choices.
So I logged into Gnome(failsafe) and got my full GUI.
Console (F1) and xterm also work fine.
Trying to get my Gnome Desktop back.
GDM is working and I have the session choice for TWM, but with Gnome(failsafe) working I haven't tried it yet to see if it works.
Did the usual checks for config files, etc.

Did you upgrade or do a clean install? Your post is not at all clear on that point.

What is your run-level?
Some how you've changed to x-desktop.
right -clicking on screen gives options.
I have debian squeeze and it's set at run-level 2 which has regular desktop.