This other thing with it not quitting/relaunching properly is still an issue. I tried clearing the library and then quitting, but then still couldn't re-open. Rebooted, restored windows library, quit, couldn't re-launch. Rebooted, got error log. (attatched).
Unfortunately, you did too much.
I want to know if:
1. You can Clear the Library and then quit MC (apparently not).
2. Force MC to quit (the easiest way will be via the
Activity Monitor, though you can also just reboot if it is really stuck).
3. Now, try to open MC. Wait a minute, and see if it closes gracefully.
It isn't that surprising that:
if the Library is corrupt, whatever process is getting stuck because of it, is
already stuck when you do the Clear Library command. So that next attempt to quit isn't very important. It is the one after that with the cleared Library that will tell us something.
So, if you do the above, and the behavior is identical (it won't quit even when started "fresh" with a cleared Library) then you KNOW it isn't related to the Library at all. You can restore your backup and ignore that.
In that case, I'd next clear Settings (the stuff in Tools > Options that is separate from the Library). I can tell you how to do that, when we get there.