login window disapears after sys update

[oxy]

Hi

I ve just done a sys-update in my Ubuntu 12.04 64Bit,
installed a week ago and pretty standard. The update
manager required a reboot, I did it and now I cannot
get the login window anymore! :-/
Just a blank window, no reaction to Ctr-Alt-F1 and so on.

I can ssh login to the system and work on it remotely.
Any help to get this login window again?

Thx