After upgrading to Ubuntu 17.10, everything worked fine. However, today I was no longer able to log in via the login screen. Confirming the password entry by pressing ENTER, I get a message saying that the password is not correct or I get an empty password field again, respectively. Nothing else happens.
I can, however, log in using the command line mode and start the Mate desktop there using startx. Once the desktop has started, desktop session GUIit will accept my password for authehticating any kind of root action.
I’d appreciate any suggestion, what may have happened.