Thank you for contacting us and for your feedback.
The installation of the latest version of the RadControls for ASP.NET AJAX
has removed your previous installed version, which has broke your project references. To
fix your project you need to open it in Visual Studio and go to Telerik-> RadControls for ASP.NET AJAX-> Upgrade Wizard. Following the wizard will fix your references.
Let us know if you need further assistance. We are constantly trying to improve our products, so please don't hesitate to share with us your feedback about our products.