Jul 13, 2012 at 1:09 AM

Contrary to this statment..

 If no 'TopLevel' property value is provided, it will infer the current site context (of web part location).

I find that not configuring the url (leaving it blank) tries to to go the top level site and errors with access denied if you don't have permissions to that site.  I have to have the Collection administrator set the url for me.