Before trying this I suggest you to close all your important things!
After this test you can reach (with a bit of luck) the terminal by pressing Ctrl+Alt+F1 to reboot your System!
For me this affects Ubuntu 14.04.5 with the Unity Desktop...
The freezing hotkeysequence is:
Ctrl+Alt+F8
Ctrl+Alt+F1
Ctrl+Alt+F7 (returns to GUI, but now is freezed)
Before trying this I suggest you to close all your important things!
After this test you can reach (with a bit of luck) the terminal by pressing Ctrl+Alt+F1 to reboot your System!
For me this affects Ubuntu 14.04.5 with the Unity Desktop...
The freezing hotkeysequence is:
Ctrl+Alt+F8
Ctrl+Alt+F1
Ctrl+Alt+F7 (returns to GUI, but now is freezed)