When the problem happens, I'm still able to alt-tab to any active windows. When I click on the Pinballx window I'm presented with the dialog box that says basically "PinballX is unresponsive. Close the program or Wait for program to respond.'. If I select close the program, which is the only option that does anything, I get another dialog box that says something like "sending information to microsoft for analysis'. One that dialog exits, I'm left with a desktop that is missing the start bar at the bottom. The top half of desktop icons are still there but not the bottom part.
I'd be more than happy to run a version of pinballx to capture more information if you want. One use case I have to try is starting pinballx but not selecting any tables to play. I'm curious if the demo mode at that point won't cause the lockup.