On several occasions, when I click on "Switch User" I would be directed to a black screen with a mouse cursor where the mouse cursor may work in a very lagging manner and nothing else seems to work(no keyboard response). To get out of this situation, I need to manually power off my system and power it up again to boot the system up again.
Sometimes this bad situation happens and sometimes I would successfully be directed to the login screen to switch users successfully.
Any idea what is causing this issue or how I can fix this issue?
[Update:] On my next bootup, I re-tried using the "Switch User" button. I got the same black screen and mouse cursor. But this time around, the default Ubuntu screensaver or screen shield appeared ( after several seconds delay ) instead of the background that I had set previously. After pressing any keyboard key, the screen shield goes away and the Login screen appears.