I got it to work again. I'm not sure how I did it, but I have a theory. My guess is that it had some invalid setting stored in memory, and after being unplugged for a while, the capacitor lost its charge, and the invalid setting faded. Then after being replugged, it re-initialized, and since the invalid setting was gone, there were no problems.
Andy, if you're reading this, you can disregard your most recent e-mail from "thecrankyhermit@hotmail.com," unless there's anything you'd like to say that you think I might find interesting or informative. In any event, consider my problem completely resolved.