Black login screem

Hi all ... ater running an "apt-get update && apt-get -y upgrade" on Terminal, I received a msg saying that something was missing (I don't remember actually the msg sorry about it) and it said that I could run the apt-get -f install" to correct it.
So I've ran it and then a red circle near the clock appeared saying that I should run an Update (something similar to the terminal command, just in a GUI version) ... and then I've ran it and rebooted my machine.

Now, everytime I turn on my notebook, the login screen statys all black. I still hear the beep sound when the login screen appears and if I type the password and hit enter I can login on Trisquel and the screen is back again.

This is not impacting me in any way, once I can still login on the system.
Any ideais of what I can do just to try to have the login screen working again?

Thanks!