Listview fails to display text of list items when item count exceeds 400 items

I can get a large amount of items to display within a Listview.

However, when I apply a DataTemplate, the listsview does not display any items.

This works:

<ListView x:Name="ContactList" ItemsSource="{Binding SelectedCategory.Contacts}"
            Height="425"
            Width="425"
            Margin="58,175,0,0"  Canvas.ZIndex="99"
            Background="Transparent" Foreground="#FF333747" 
            VerticalAlignment="Top" HorizontalAlignment="Left">

    <ItemsControl.ItemsPanel>
        <ItemsPanelTemplate>
            <VirtualizingStackPanel />
        </ItemsPanelTemplate>
    </ItemsControl.ItemsPanel>

    <ItemsControl.Template>
        <ControlTemplate TargetType="ItemsControl">
            <Border>
                <ScrollViewer>
                    <ItemsPresenter/>
                </ScrollViewer>
            </Border>
        </ControlTemplate>
    </ItemsControl.Template>

    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <TextBlock Text="Hello Wworld" />
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ListView> 

This doesn't:

<ListView x:Name="ContactList" ItemsSource="{Binding SelectedCategory.Contacts}"
            Height="425"
            Width="425"
            Margin="58,175,0,0"  Canvas.ZIndex="99"
            Background="Transparent" Foreground="#FF333747" 
            VerticalAlignment="Top" HorizontalAlignment="Left">

    <ItemsControl.ItemsPanel>
        <ItemsPanelTemplate>
            <VirtualizingStackPanel />
        </ItemsPanelTemplate>
    </ItemsControl.ItemsPanel>

    <ItemsControl.Template>
        <ControlTemplate TargetType="ItemsControl">
            <Border>
                <ScrollViewer>
                    <ItemsPresenter/>
                </ScrollViewer>
            </Border>
        </ControlTemplate>
    </ItemsControl.Template>

    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding DisplayName}" />
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ListView> 

It appears that displaying listview items using a data template fails once a binding is applied. How can I resolve this?