On Windows 7-64 in a Virtualbox, running MG in full screen, I set a new resolution using the options menu. What happened is that my screen went black despite of the Windows "busy" (like hourglass) mouse pointer was still drawn, the game music continued to play, and Windows still seemed to react generally. however many options I tried to get MG or just the desktop back into a usable state, failed, and the only option remaining was to make Virtualbox shut down this guest with ACPI (which worked). I can try windowed another day.