XAML Button event handlers not firing in Beta 2

After converting my Beta 1 application and fixed any compile problems I can't seem to get my XAML declared event handlers to fire. Here is an example: 
 XAML:
<Button x:Name="btnBack" Grid.Row="5" VerticalAlignment="Bottom"
        HorizontalAlignment="Stretch" Margin="20,0,64.5759963989258,0" d:LayoutOverrides="GridBox" MouseLeftButtonUp="btnBack_MouseLeftButtonUp" Template="{StaticResource ButtonControlTemplate2}" Height="50"></Button>
            
 Code Behind:
        private void btnBack_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
        {
            TransitionBase transition = new FadeTr ...