I use Ubuntu on a Lenovo Thinkpad X1 laptop and sometimes Gnome becomes unresponsive after sleep mode. The system is working, but I can’t see anything except for the cursor on the black screen.
In these cases the only solution I found was to access
tty1 by pressing
ctrl+alt+f1 and restart the system by running
sudo shutdown -r now.
A better solution when Gnome crashes is to restart only the window manager, not
the whole system. To do so you can use the shortcut
alt+stamp+k to restart
Gnome and the problem is solved, unfortunately any unsaved file will be lost.