Oh, not yet! I need to do that right quick. Lemme try again...
Quick explanation, parts of UTAU's inner workings contain characters that can get corrupted and cause problems like random silence and errors if you DL and install outside of Japanese locale. That's the reason you need locale, rather than just so Japanese voice banks and USTs will work (though that's a bonus).
Going off of what Halo said (and I'm not entirely sure this is correct, so please correct me if I'm wrong), I'm assuming that you may have to reinstall the plugin if your locale wasn't updated because of the internal data being corrupted