Are you using the default theme?
Try Ctrl-Alt-F1 to get to a console. If you see a login prompt, log in, then
1. see if you had any errors
Code:
cat /var/log/Xorg.0.log | grep EE > xorg-errors.txt
2. change your driver to the new nouveau driver (2D accel, but no 3d) by editing the X config file. Type:
Code:
sudo nano /etc/X11/xorg.conf
In that file, look for
and change it to
Save the file (CTRL-X).
3. restart your xserver
4. paste the contents of xorg-errors.txt here