Great idea! So, as it turns out, I don't get the javascript error when adding the "showIf" behavior to a "blank" PHP page containing only the form. (I've attached that page as "formTest.php".)
However, when I try taking out ALL php and javascript code on my original form page, I continue getting the "showIf" javascript error. I have also attached my "stripped down" communicationForm3.php page.
Everything else on the page is really standard stuff. I can't imagine any of it causing a conflict... but who knows. This is really strange.
Any other ideas? Thanks again!
Jeremy