Could not load file or assembly 'System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies

The following error:

Could not load file or assembly 'System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.
 

indicates that the web application is looking for AJAX version 1.0.61025.0.  Our servers have AJAX version 3.5 or higher installed. You will need to update your application so that it calls on the correct AJAX version for your server, and not version 1.0.61025.0.