Just a couple of things. If I shut down from task manager, it seems to work, at least to the point of being able to re-start X2.
Moving sideways, is it possible to have no MIDI output devices defined under Preferences>MIDI>Devices? The reason I'm asking is that, as I looked through different settings, I found that the only MIDI output device that I have listed is the Microsoft GS Wavetable Synth, which is checked. I never use it, but it is checked anyway, so I tried to uncheck it. The little eternal circle spins and spins until you give up and click in X2 somewhere and then it tells you that X2 is not responding. Could this be what is not allowing X2 to shut down, or is having at least one MIDI instrument required?