The example works wonderfully for me (Supplied Project)...
I understand I need to put the code below at the TOP PAGE, which I did.
My RADHTMLPlaceHolder is inside a TAB which is inside a pane.
So, then I try
silverlightApplication = parent.GetSilverlightApplication();
it was returning me a null pointer as parent is not the RootVisualTab.
===== CODE FOLLOWS =====
public void HandleOutSideClick()