We are not aware of such an issue related to the Blend support for RadControls/Silverlight.
Since you have added the full list ot references related to any RadControl you should not get such an error. May you please share with us a bit more details about the problem you have experienced in Expression Blend and which RadControls you are currently using? Furthermore you may also submit a new support ticket and attach a runnable project where we can see what might be wrong.
the Telerik team
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