Thank you for writing.
I order to help you I would ask you share with us more details about this exception?
When exception is thrown: In design-time or in run-time?
- If this happens in design-time, could you rebuild the project, restart the Visual Studio and try again to reproduce the exception.
I am looking forward for your response.
the Telerik team
Check out Telerik Trainer
, the state of the art learning tool for Telerik products.