Black Box Window on OOB Application In Full Screen Mode

I have an SL5 Out of Browser Application (Runs in Elevated Trust). In the OOB SL5 app when the user clicks a button, the application appears in Full Screen mode. This works fine.  However, on the task bar, another icon appears. Clicking on this icon causes a small black box to appear.  If I close the black box, my OOB application closes.  The user can select the black box from the task bar. Or press alt tab and view the black box. This black box gets in the way of the application.  It only appears when the application is in full screen mode. Is there any way to remove this black box or make it unselectable?

xaml

<Grid x:Name="LayoutRoot" Background="White"><Grid.RowDefinitions><RowDefinition Height="40" /><RowDefinition Height="40" />           </Grid.RowDefinitions><sdk:Label Content="Hello, World" FontSize="18" FontWeight="Black" HorizontalAlignment="Center"/>       <Button Grid.Row="1" Click="Button_Click" Width="100" Height="25" Content="Full Screen" /></Grid> 

C#

  public partial class MainPage : UserControl
    {
        public MainPage()
        {
            InitializeComponent();
        }
        private void Button_Click(object sender, RoutedEventArgs e)
        {
            Application.Current.Host.Content.IsFullScreen = true;
        }
    }