Error Creating Control - Failed to create designer 'Telerik.Web.UI.

Telerik Error Creating Control,Error Creating Control Failed to create designer, Telerik Design time error,RadControls
You’ll find this error from time to time when switching to Design View in Visual Studio to work with Telerik Radcontrols, especially after Upgrading to a new version of Telerik UI for ASP.NET Ajax.

Causes:

• There is a GAC-reference for the Telerik.Web.Design assembly in the project and the      GAC has been updated. As a result, the Telerik.Web.Design assembly, referenced by the WebSite, does not exist in the GAC.
• The reference to the Telerik.Web.UI assembly (either in Register directive or web.config, or Telerik http handlers/modules registrations in web.config) contains hard-coded version number which does not match the version of the Telerik assembly referenced in your project.
• Open the application in a machine that doesn't have Telerik UI Installed.

Fortunately there are several ways to solve this problem:

• GAC Deploy the required version of the Telerik.Web.Design.dll.

The Telerik.Web.Design assembly contains the Visual Studio designers of the controls. 

          Telerik.Web.UI.dll requires Telerik.Web.Design.dll of the same version in the GAC.

Use the command gacutil /i [path to Telerik.Web.Design.dll with latest version]

• Bin-deploy the design-time assembly Telerik.Web.Design.dll

Remove Telerik.Web.Design.dll from the GAC

Copy Telerik.Web.Design.dll to the bin folder

          Restart Visual Studio

• Bin-deploy the assembly Telerik.Web.UI.Skins.dll

Copy Telerik.Web.Skins.dll to the bin folder
          Restart Visual Studio

• In web.config file, removing the specific version, Culture, and PublicKeyToken from the Telerik.Web.UI.WebResource.axd entry.

         Correct Syntax:
        <add path="Telerik.Web.UI.WebResource.axd" type="Telerik.Web.UI.WebResource" verb="*"   validate="false"/>

The second solution did the trick for me. Hopefully one of the above solutions will work for you.