As described in your corresponding support thread, I would recommend to ensure that the same version of our controls is loaded in the toolbox and referred in your project.
To do this, please follow the steps bellow:
- Open the Configure Wizard (documentation: http://www.telerik.com/help/winforms/installation-deployment-and-distribution-vsx-creation-and-configuration-wizard.html) and check the version of the distribution used by the project
- Start the Toolbox Configurator (documentation: http://www.telerik.com/help/winforms/installation-deployment-and-distribution-vsx-toolbox-configurator.html) and ensure that the same version in loaded in the toolbox
the Telerik team