I created a silverlight app (without website) named TestApp, with one TextBox:

<UserControl x:Class="TestApp.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
    mc:Ignorable="d" d:DesignWidth="640" d:DesignHeight="480">
  <Grid x:Name="LayoutRoot">
        <TextBlock Text="this is a test"/>
  </Grid>
</UserControl>

I press F5 and see "this is a test" in my browser (firefox).

I select File | Export Template | name it TestAppTemplate and save it.

I create a new silverlight app based on the above template.

The MainPage.xaml has the exact same XAML as above.

I press F5 and see a blank screen in my browser.

I look at the HTML source of both of these and they are identical.

Everything I have compared in both projects is identical.

What do I have to do so that a Silverlight application which is created from my exported template does not show a blank screen?

(creating a WPF application from an exported template like this works fine)