In Kentico version 6.0, it is giving error
[NullReferenceException: Object reference not set to an instance of an object.]
   CMS.PortalControls.CMSAbstractEditableWebPart.LoadContent(PageInfo pageInfo, Boolean forceReload) +88
   CMS.PortalControls.CMSAbstractEditableWebPart.LoadContent(PageInfo pageInfo) +43
   CMS.PortalControls.CMSPagePlaceholder.LoadRegionsContent(Boolean loadChildren) +186
   CMS.PortalControls.CMSPagePlaceholder.OnLoad(EventArgs e) +67
   System.Web.UI.Control.LoadRecursive() +74
   System.Web.UI.Control.LoadRecursive() +146
   System.Web.UI.Control.LoadRecursive() +146
   System.Web.UI.Control.LoadRecursive() +146
   System.Web.UI.Control.LoadRecursive() +146
   System.Web.UI.Control.LoadRecursive() +146
   System.Web.UI.Control.LoadRecursive() +146
   System.Web.UI.Control.LoadRecursive() +146
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2207