title: After Windows Phone App comes back from Tombstone App.RootFrame.Navigate(uri) doesn't work
body: <p>I have an app that works just fine.  But if I launch launch any one of the tasks (WebBrowserTask, SendEmailTask etc) I get tombstoned.  When I finished the task the App restores just fine but the Navigate() calls don't work anymore.  Meaning that the code runs but nothing happens, all navigation is broken from then on.</p>
  
  <p>Here's the code I use to navigate:</p>
  
  <pre><code>((App)App.Current).RootFrame.Navigate(new Uri("/MyPage.xaml", UriKind.Relative));
  </code></pre>
  
  <p>I'm handling the NavigationFailed event as well and that never gets fired... </p>
  
  <pre><code>((App)App.Current).RootFrame.NavigationFailed += RootFrame_NavigationFailed;
  </code></pre>