BrightAuthor doesn't show files I recently added to the Media Library

I can't get either the file sub-window or the presentation sub-window to update in the Edit tab when I replace a JPEG with a new version of the same name. I can close the application and re-open it, navigate to a different folder and navigate back, click the refresh button, nothing seems to replace the thumbnails in these displays with the new content. However, if you delete the old slide from a presentation and then drag what *appears* to be the old one back into the presentation, the published version shows in the output with the correct version of the pic. I suppose a work-around is to rename the new slide, then replace the old page that way, but there really ought to be a way to refresh the thumbnails! (BA 3.8.0.41 on Win 7)