Invalid XAML if I use RadGridView in a DataTemplate?

[Rob Ainscough]

VS 2010 is generating an error that I have "Invalid XAML" ... I've pin pointed the error directly related to Telerik RadGridView being part of a DataTemplate.

<DataTemplate x:Key="MarketingAnswersDataTemplate">
    <Grid Width="650">
        <telerik:RadGridView ShowGroupPanel="False"
                             RowIndicatorVisibility="Collapsed"
                             Margin="8"
                             DataContext="{Binding Source={StaticResource MarketingAnswersData}}"
                             ItemsSource="{Binding Collection}"
                             AutoGenerateColumns="False">
            <telerik:RadGridView.Columns>
                <telerik:GridViewDataColumn Header="Answers"
                                            MaxWidth="100"
                                            MinWidth="100"
                                            Width="100"
                                            DataMemberBinding="{Binding MarketingID}"
                                            IsVisible="False" />
                <telerik:GridViewDataColumn Header="Answers"
                                            Width="300"
                                            DataMemberBinding="{Binding MarketingAnswer}" />
                <telerik:GridViewColumn  FooterTextAlignment="Center"
                                         IsResizable="False"
                                         IsGroupable="False"
                                         IsFilterable="False"
                                         MaxWidth="30"
                                         MinWidth="30"
                                         TextAlignment="Center"
                                         Width="30"
                                         Background="Transparent"
                                         HeaderTextAlignment="Center"
                                         IsSortable="False"
                                         IsReorderable="False"
                                         ShowDistinctFilters="False"
                                         CellTemplate="{StaticResource MyAppDeleteMiniButton}" />
            </telerik:RadGridView.Columns>
        </telerik:RadGridView>
        <Button Content="+"
                HorizontalAlignment="Right"
                Margin="0,11,30,0"
                Width="24"
                FontWeight="Bold"
                VerticalAlignment="Top"
                Canvas.ZIndex="1"
                Padding="0"
                Height="22"
                FontSize="21.333"
                ToolTipService.ToolTip="Add a Discount"
                Cursor="Hand"
                FontFamily="Arial"
                Template="{StaticResource MyAppGreenAddButton}">
            <Button.Background>
                <SolidColorBrush Color="#FF1F3B53"
                                 Opacity="0.715" />
            </Button.Background>
        </Button>
    </Grid>
</DataTemplate>

If I remove the Telerik:RadGridView, this will clear VS 2010 "Invalid XAML" error.  

NOTE: Blend 4 does NOT generate any "Invalid XAML" error, this is ONLY in VS 2010.  Also, my application runs fine with in both VS 2010 and Blend 4.  But because of this error the VS 2010 designer is unable to load and display the XAML.

Is this a know BUG?  Any work around?

Thanks, Rob.