I'm running LR CC on Win10, and I was exporting photos normally when my computer crashed from what I think was an overheat.
I rebooted, deleted the photo files that had been made in the filesystem but not fully created (about 6 of 12), and then attempted to re-export. When I went to choose the specific folder (in Choose Later), the Choose Folder window appeared to be responsive for about half a second, then froze. In that state, I'm unable to press Cancel or select any folder at all, or close Lightroom short of force-closing it via the Task Manager.
I've tried the following, and these didn't help:
However, any option that does not require me to open the Choose Folder window seems to work fine. So, for now I'm exporting to My Documents and moving them manually from there.
Okay, so I fixed it.
I just tried to re-export the files that had failed initially using the My Documents folder export. That worked. Then I went to export something else, and the Choose Folder window now takes input and doesn't crash the butt out of my LR.
So for anyone else who has this problem, Merry Christmas.