I suppose that your application uses Telerik controls that have references to Telerik.Windows.Controls.Input.dll, for example such controls are RadScheduler and RadGridView. If you do not reference the Telerik.Windows.Controls.Input.dll you could get that exception. Other reason could be mixed versions of the Telerik assemblies, e.g. Telerik.Windows.Controls.Input.dll is older than the rest of the assemblies. A sample application could be of great help for the resolution of this problem.
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