If I have this in XAML
<Controls:ImageButton Grid.Row="0" Grid.Column="0" HorizontalAlignment="Center" VerticalAlignment="Center" NormalStateImageSource="Content/Images/TowerPlayerENUS.png" GenerateMissingImages="True" />
When either in the VS XAML designer or Blend Designer will crash with:
FileNotFoundException: The system cannot find the file specified. (Exception from HRESULT: 0x80070002)
It is happing in the IO component.
However, if the NormalStateImageSource is not set, it works fine.
Probably should just put a try catch around it instead of trying synchornize everything that is going on.