         
         if (instance == columnHeaderBar)
         {
-            columnHeaderBar.dataProvider = null;
             columnHeaderBar.horizontalScrollPosition = 0;
             columnHeaderBar.owner = null;
         }

            initializeGridRowBackground();
        
        if (instance == columnHeaderBar)
        {
            columnHeaderBar.dataProvider = columns;
            columnHeaderBar.owner = this;
        }
    }
    
    /**

    public function set columns(value:IList):void
    {
        if (setGridProperty("columns", value))
        {
            if (columnHeaderBar)
            {
                columnHeaderBar.layout.clearVirtualLayoutCache();
                columnHeaderBar.invalidateSize();
                columnHeaderBar.invalidateDisplayList();
            }
            
            dispatchChangeEvent("columnsChanged");
        }
    }
    
    /**
