Sorry. Let me try to be more precise. First off, this is the very first thing I did when mp3ts started for the first time. I ran the program for the first time (I don't remember if I let the installer run it or if I ran it myself, but I don't think it makes much difference, since it always does this), and it popped up the first run dialog (I forget now what it says) and I clicked okay. The tab that was on top by default was the Auto Write Tags Based On Filenames tab. The first thing I noticed was that the templates were back to your defaults (as I expected). I usually remove them and add my own. So I clicked the minus button. It didn't really give me any feedback, but when I click the down-arrow button on the dropdown box, the one listed in the normally visible area was gone, although it was still listed in the visible area. I moved the mouse to select the other default template. (This was not a click-and-drag motion; it was a click-and-release followed by a move.) When the mouse pointer entered the area where it would normally highlight the top choice, I got that error dialog. As far as I can tell, it never highlighted it. I've doublechecked 2.18 on the same computer and it definitely doesn't have the same problem.

Speaking of which, it's slightly annoying to have to uninstall the old one to install the new one, especially for testing purposes. But it's not a big deal.