ListPicker in a ListBox. Only the first one work

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Windows

XAML

Silverlight

phone

I have a ListPicker in the ItemTemplate of a ListBox, like this:

<!-- SubTaskSet = 3 Items -->
<Grid x:Name="ContentPanel" Margin="0,0,0,12" Grid.Row="1">
    <ListBox x:Name="MainListBox" Margin="0,0,0,0"
                Height="577" 
                ItemsSource="{Binding SubTaskSet}"
                ItemTemplate="{StaticResource TESTListItemTemplate}"> 
    </ListBox>
</Grid>

And the TESTListItemTemplate look like this:

<DataTemplate x:Key="TESTListItemTemplate">
    <Grid HorizontalAlignment="Stretch" Width="500">

        <toolkit:ListPicker ExpansionMode="FullscreenOnly">
            <sys:String>dark</sys:String>
            <sys:String>light</sys:String>
            <sys:String>dazzle</sys:String>
            <toolkit:ListPicker.FullModeItemTemplate>
                <DataTemplate>
                    <StackPanel Orientation="Horizontal" Margin="16 21 0 20">
                        <TextBlock Text="{Binding}"
                                Margin="0 0 0 0"
                                FontSize="43" 
                                FontFamily="{StaticResource PhoneFontFamilyLight}"/>
                    </StackPanel>
                </DataTemplate>
            </toolkit:ListPicker.FullModeItemTemplate>
        </toolkit:ListPicker>

    </Grid>
</DataTemplate>

But only the first ListPicker in the ListBox work as expected, the next 2 is dead.

I have just updated the ToolKit to version August 2011. Before I used Nov. 2010 and everything worked fine. Is this perhaps a bug in the new ToolKit?