Since Q1 2009, the RadControls for ASP.NET AJAX installer includes Visual Studio Extensions - a Visual Studio integration package, aiding the creation/modification/upgrade of projects/websites, using RadControls for ASP.NET AJAX. The main assembly of the integration package is the Telerik.Web.UI.VSX
assembly. There should be the Telerik.VSX
assemblies in the GAC too. As the VSExtensions are not .NET Framework dependent, the version ends with 0.
Another thing to mention is that the installer does not add the Telerik.Web.UI
assembly automatically to the GAC. Please, add it manually instead.
I hope this helps.
the Telerik team