OK, after about six hours at the machine, I figured it out.
While reading a different forum, I saw the CSSMenuWriter folder discussed and realized I needed to upload it to my site. That solved it.
Could I suggest adding a line to the getting started guide to tell people this crucial step? I didn't even know there was a CSSMenuWriter folder. I've never written a javascript, and when I've used widgets before (such as in blogger), they were hosted at the app's site, I guess. Or they told me what to do.
Why leave one of the required steps out of the How To guide?