This is a report of a bug in the PM contact sheet browser.
This is how to reproduce the bug.
1. create a directory tree:
/topdirA
/topdirB
/topdirB/subdir1
/topdirB/subdir2
/topdirB/subdir2/...two or three image files, number doesn't matter.
2. Open Photo Mechanic, use browser to find and open /topdirB/subdir2
3. Close the contact sheet that is open, close PM.
4. Use windows (I am using win7) file explorer to drag ../subdir2 to another directory...like /topdirA. Just so it isn't in /topdirB any longer.
5. Open PM and the PM browser will lockup because it can't find /subdir2 any longer and it remembers /subdir2 (a feature that I like BTW).
6. With PM closed use win explorer to move /subdir2 and its files back to /topdirB so the browser can find it.
7. Open PM again and everything should work fine. If you then select another dir in the PM browser (like /subdir1) and then close PM and move /subdir2 to a new location, PM won't lock up when opened.
That's it.