I have to add a similar problem.
If i remember it correctly, i have this problem since MC 18, 19, 20.....
Using BlackonBlack Skin. Pressing analyze audio (Standard View) in settings completely stops mc responding to any key anymore, because analyze audio popup window opens and disappears in the background (losing focus/completely empty window).
This happens since a long time ago at home on three different machines (No Antivirus Tool installed).
Not happening all the time, but very often.
And i have the same problem as the Threadstarter described. Also since MC 18.