Hi, we have just had this error message, which we are unsure why it happened. The only way we could fix it was to upload the web.config file to reboot the system. Sitefinity is working again but we would like to know why this may have happened. All we did was add a user to the backend.
Thanks,
O.
Server Error in '/' Application.
Cannot create an instance of Telerik.Sitefinity.Web.UI.ContentUI.Config.ContentViewDefinitionElement because it is an abstract class.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: System.MemberAccessException: Cannot create an instance of Telerik.Sitefinity.Web.UI.ContentUI.Config.ContentViewDefinitionElement because it is an abstract class.