Hello,
This can be resolved by either uploading the system.web.extensions.dll file into the bin folder of your website (all servers), or if you are on one of our Windows 2003 servers (win2, win5, win11 and win16 through win30) you could modify the code for that to utilize the version of AJAX included with ASP.NET 3.5. Please note that for this latter solution, if your account is on win5, win11 or win16 through win18 you would also need to have your domain manually upgraded to ASP.NET 3.5 by our staff via a support ticket entered from within your Servergrid control panel.