If you turn off the automatic refreshing in the Navigator, it becomes much more stable. Right click on a folder in the Navigator, go to the Photo Mechanic sub-menu, and disable the Auto Refresh option.
Well, I tried this and the problem actually got worse. If I turn off auto refresh without any contact sheets open, it crashes after opening 2-3 folders. If I turn off auto refresh with contact sheets already open, it crashes immediately. Consistently.
Not that it will necessarily help, but this message also shows up (I don't recall anyone else reporting it):
The instruction at "0x7c2821b2" referenced memory at "0x0000001c". The memory could not be "read".