I have similar issue for my ubuntu:Ubuntu suddenly goes Black Screen
The system can normally boot into the GUI and I can use it for few hours. It just suddenly went black screen and it happened couple of times since my last update/upgrade.However, I tried take control this morning by pressing Ctrl+Alt+F2 and I found login prompt pop up. So, it is not a total system crash. It seems like some desktop package crash.
Does anyone know how to do inspection and fix it?Thanks.