XamlParseException due to DatePicker from WPFToolKit

Error : UnhandledException: System.Windows.Markup.XamlParseException: '/WPFToolkit;component/DataGrid/Themes/Luna.NormalColor.xaml' value cannot be assigned to property 'Source' of object 'System.Windows.ResourceDictionary'.

Could not load type 'System.Windows.Controls.Primitives.MultiSelector' from assembly 'PresentationFramework, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'.  Error at object 'System.Windows.ComponentResourceKey' in markup file 'WPFToolkit;component/DataGrid/Themes/Luna.NormalColor.xaml'.  Error at object 'System.Windows.ResourceDictionary'. ---> 

System.Windows.Markup.XamlParseException:  Could not load type 'System.Windows.Controls.Primitives.MultiSelector' from assembly 'PresentationFramework, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'.  Error at object 'System.Windows.ComponentResourceKey' in markup file 'WPFToolkit;component/DataGrid/Themes/Luna.NormalColor.xaml'. ---> 

System.TypeLoadException: Could not load type 'System.Windows.Controls.Primitives.MultiSelector' from assembly 'PresentationFramework, Version=3.0.0.0, C开发者_JAVA技巧ulture=neutral, PublicKeyToken=31bf3856ad364e35'.

I keep getting the following exception. I am getting the exception when I run the application exe from the Release folder. I do not get the exception at all when normally debugging the application in Visual Studio. I have worked out that the exception is because of a DatePicker control I am using - as if I remove the control (build and run the release exe again) the exception goes away.

How on earth could I work out what is going wrong here?

The datepicker looks so much better but for the effort this looks like it might be to fix I may be incline to switch for a textbox which I validate when the submit button is pressed! Dissapointing...

The problem was due to the testing machine having .Net Framework 3.5 and not 3.5 SP1. Upgrade to 3.5 SP1 fixed the problem.