After installing display drivers for my HD 6450 Gnome-shell failed to start up.
The solution for me:
Go to the AMD site and download this file.
Right click it and make it executable. Run it.
Download and install the AMD drivers with YaST. I think you may have to add the repository below.
Index of /mirror/ati/openSUSE_12.1
Next open a Terminal window and run
aticonfig --initial
Reboot.
It worked for me! rotfl!