I have created a NavigationPane just like Outlook 2007. Here when the Pane is collapsed and the side bar is clicked, Outlook used to popup the Selected NavigationItem content. I mimicked like the same using to contentpresenter in the ControlTemplete (one for the TabControl's SelectItemHost and another for the Popup). But the problem is when the Popup is open up, the NavigationPane selected content when away and it appears when we switch back to the same navigation item from another navigation item. I am using TabControl and TabItem as NavigationPane and NavigationPaneItem.
I am pointing the "SelectedContent" as the ContentSource for the two ContentPresenter