I finally got the chance to try the new build. Sadly, it's still blocking me from logging off until I kill the process in Task Manager or right-click and exit. Also, it got way bigger!

Happens every time, it's definitely reproduceable for me. I very rarely take a screenshot (once every two or three days), so I doubt it's holding any file handles open when I try. I tend to turn the laptop off about once every day.

I'll be shutting down again in about five or six hours; is there some way of asking Windows whether Screenshot Captor has any files open?

Wouldn't it be awesome to have Mac-like spring-loaded folders on Windows? You grab a file, drag it, hover on a folder for 2 seconds, an Explorer window opens. Hover on a folder in there, another opens, until you've navigated to the destination folder, where you can drop off your file. As soon as you let go the mouse, all the Explorer windows that opened spring shut again. This requires writing an Explorer extension.