there is actual a failure in update. Kernel conflict with Nvidia.
I have seen that on 2SLED and 1 SLES.

What to do:
Ctrl+Alt+F1 get to a screen.
Login as root
type yast
search for Nvidia
update all drivers, but mark them from bottom up - not up - down.
After update of driver close Yast
type startx

now the screen is back.