When I compiling the sample project SLARToolKit3DSample, the ide output an error below:

Error 4 'System.Windows.Media.Media3D.Matrix3D' does not contain a definition for 'ToXnaMatrix' and no extension method 'ToXnaMatrix' accepting a first argument of type 'System.Windows.Media.Media3D.Matrix3D' could be found (are you missing a using directive or an assembly reference?) D:\AR\slartoolkit-72933\trunk\SLARToolKit\Source\SLARToolKit3DSample\MainPage.xaml.cs 211 64 SLARToolKit3DSample

I have installed vs2010 with sp1,  silverlight4&5,  directx SDK, and any other SDK need?