[InvalidOperationException: Only one instance of a ScriptManager can be added to the page.]
System.Web.UI.ScriptManager.OnInit(EventArgs e) +452120
System.Web.UI.Control.InitRecursive(Control namingContainer) +139
System.Web.UI.Control.InitRecursive(Control namingContainer) +312
System.Web.UI.Control.InitRecursive(Control namingContainer) +312
System.Web.UI.Control.InitRecursive(Control namingContainer) +312
System.Web.UI.Control.InitRecursive(Control namingContainer) +312
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +408