Thanks so much for your time and help.

Sorry, I understand that the error message should be hidden by default and that JS would be showing it when it feels it is necessary.  I guess my question is - what configurations do I have to make in DNN so that it knows what that necessary condition is?  I want to tell it , "not only is this field required, but you must pick the TRUE option and not the FALSE option for this to be considered a valid form."  Is that what selecting  a TRUE/FALSE required custom field does by default?

By "enable show script errors," do you mean have the developer tools open in the browser and show the console tab?  If so, I am doing that with Chrome and not getting any errors logged to the console.  I have just verified that this is also the case for Firefox and IE.  If you meant something different, how do I go about doing what you're saying?

I can get on board with the theory that some external JS is affecting this page.  During the upgrade process, I was pleasantly surprised at how smoothly the VB and other code transferred, until I ran into all sorts of custom JS issues.  I learned all kinds of things about JavaScript I never knew, like referring to data attributes used to be case insensitive, and how to make web service calls pre-AJAX!  I ended up having to rewrite all of that, but everything except this page seems to be functioning pretty well.  

I think a good next step would be to try disabling any external JS references one by one and see if I can isolate the cause.  If you can think of anything else I need to configure DNN-wise, please let me know.

Thanks again!