Controls Not Compatible with RadAjax
The following ASP.NET controls are not compatible with partial-page updates, and are therefore not supported inside anUpdatePanel control:
Web Parts controls. For more information, see ASP.NET Web Parts Controls.
FileUpload controls when they are used to upload files as part of an asynchronous postback.
GridView and DetailsView controls when their EnableSortingAndPagingCallbacks property is set to true . The default is false .
Login, PasswordRecovery, ChangePassword, and CreateUserWizard controls whose contents have not been converted to editable templates.
The Substitution control.
See a full list of controls that are not compatible with RadAjax for ASP.NET AJAX from the official Microsoft AJAX documentation here (scroll about halfway down the article.)).