Hi,
I was having the same problem as mentioned by Ben with "Telerik_RadControls_for_Silverlight_Beta2_Trial" .
I took the latest download "Telerik_RadControls_for_Silverlight_RC0_Trial".
Now I am not able to drag the TabControl on the Expression Blend 2.5 June 2008 preview. Every time I do it, I get the following error :
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Target Invocation Exception
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Inner exception: System.TypeInitializationException: The type initializer for 'Telerik.Windows.Controls.RadTabControl' threw an exception. ---> System.MissingMethodException: Method not found: 'Void System.Windows.PropertyMetadata..ctor(System.Object, System.Windows.PropertyChangedCallback)'.
at Telerik.Windows.Controls.RadTabControl..cctor()
--- End of inner exception stack trace ---
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OK
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I have silverlight 2 Beta 2 on my machine and for Telerik have the dlls from the download of "Telerik_RadControls_for_Silverlight_RC0_Trial".
Regards,
Sandeep