OK…I’m kind of stumped now…
1. I’ve disabled pretty much everything at this point, but if I run it through W3C Validator…there’s a bunch of unclosed tags.
2. I have another GP test install at http://spmschool.saintpiomedia.com with very similar settings (except the full screen setup in the page settings) and there are no unclosed elements at W3C Validator. (Plus, this other site has all of my plugins enabled.)