The file's there; it's got a popuptheme.rc that's included in the theme.rc, and it's got that line in it. And I still don't have a theme popup. I've checked a couple themes, and this is true for all of them. (FWIW, I had the same problem on a different machine, too, so it's not a quirk of this computer.)

Since we seem to have a new beta build out, I think I'll try installing that and see if it helps at all. Thanks for trying to help! (Edited: nope, hasn't helped.)