>If it's hidden, then the thisform.release in my close method is not actually working. I've stepped through the code, and it definitely hits that line. If there are no object references, how can it still be there?

Somewhere outside the form object is a reference to the form object; since it still exists, the form never really destroys itself, and you're left with the inevitable dangling object ref. Classically, launch non-modal form1, and from within non-modal form1, open non-modal form2, passing a reference to form1. form2 saves the reference to a form property. Non-modal form1 tries to release itself, but the object ref from form2 sustains it, so it never completes it's release...

>Deri