Applying any theme causes DataTemplate to fail

I have working code that pulls data from a ViewModel and then displays it in my View by means of a DataTemplate. Whenever I apply a Theme using ThemeManager, my DataTemplate Fails. I am just applying the Actipro supplied themes.

My XAML is nothing special

<docking:ToolWindow Title="Test" x:Name="testToolBar" Width="200">
                        <ListView Name="testListView" DataContext="{Binding Source={StaticResource TestTypeViewModelDataSource}}" ItemsSource="{Binding AvailableTest}" HorizontalContentAlignment="Stretch">
                            <ListView.ItemTemplate>
                                <DataTemplate>
                                    <StackPanel HorizontalAlignment="Center" ToolTip="{Binding TestDescription}" Margin="0,5" Height="70">
                                        <Image Source="{Binding TestIcon}" Width="50" Stretch="UniformToFill"/>
                                        <Label Content="{Binding TestName}"/>                                        
                                    </StackPanel>
                                </DataTemplate>
                            </ListView.ItemTemplate>
                        </ListView>
                        
                        
                    </docking:ToolWindow>

 In my App.xaml.cs code I have basic Theme assignment.

protected override void  OnStartup(StartupEventArgs e)
        {
 	        base.OnStartup(e);
           ThemeManager.BeginUpdate();

           try
           {
               ThemesOfficeThemeCatalogRegistrar.Register();
               ThemeManager.AreNativeThemesEnabled = true;

               ThemeManager.CurrentTheme = ThemeName.AeroNormalColor.ToString();
           }

           finally
           {
               ThemeManager.EndUpdate();   
           }


           

        }

 If I leave out the ThemeManager.EndUpdate(), My DataTemplate works fine.

Any suggestions?