DotNetNuke Error: - Version 05.00.00

System.NullReferenceException: Object reference not set to an instance of an object. at DotNetNuke.UI.Utilities.MSAJAX.Serialize(Object Obj) at DotNetNuke.UI.Utilities.ClientAPI.SerializeClientVariableDictionary(Page objPage, Dictionary`2 objDict) at DotNetNuke.UI.Utilities.ClientAPI.CAPIPreRender(Object Sender, EventArgs Args) at System.Web.UI.Control.OnPreRender(EventArgs e) at System.Web.UI.HtmlControls.HtmlInputHidden.OnPreRender(EventArgs e) at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)