Well, that was weird. I expanded all the sections, made a change, clicked on the button, and the page went to the General Settings section. Under Contact Link Type, there was a popup with the words "Enter URL". The radio button labeled Forum Email Address was selected. The next line says Contact URL. That box had the email address in it. That was what was causing the error. Once I removed the email address, the error went away and the page saved as expected.
The strange thing is, I would assume that the email address has been there all along. It simply didn't generate an error until you switched the form to html5. Lesson learned.
