Unfortunately, support for Visual Studio 2005 has been discontinued since 2012 Q1
. You can either switch to Visual Studio 2008 if that is possible or use an older version of RadControls.
Don't hesitate to write if you have any more questions.
the Telerik team
If you want to get updates on new releases, tips and tricks and sneak peeks at our product labs directly from the developers working on the RadControls for ASP.NET AJAX, subscribe to their blog feed