Upgrading Windows Phone 7.1 app to Windows Phone 8, RootFrame causes Unhandled Exception

If you are upgrading your Windows Phone 7.1 app to Windows Phone 8 and happen to be using transition frame animations built into the Windows Phone Toolkit, you may get an Unhandled Exception, which can be traced back to RootFrame navigation.

To address this problem, open the App.xaml.cs file and remove the TransitionFrame statements from the App() method, and replace the RootFrame statements in the private void InitializePhoneApplication() method with them.