John posted a comment on a wiki page

Novice query Saw error posted by another user - because they are running the program while they have their mp3 file open somewhere else, an easy thing to overcome when one reads the error and closes the other app that has the music file open. Here is another inconvenience but not a show stopper. Attached Exception happens at the end of the run for lyrics tagger could be ignored I assume it's just trying to update the progress bar and it doesn't know its finished. Just annoying but not a show stopper....