      */
     override protected function mouseDownHandler(event:MouseEvent):void
     {
-        if (!tween)
+        if (!tween && visibleColumns && visibleColumns.length > 0)
         {
             super.mouseDownHandler(event);
             updateSelectedCells();

     */
    override protected function mouseUpHandler(event:MouseEvent):void
    {
        if (!tween)
            super.mouseUpHandler(event);
    }


     */
    override protected function mouseDoubleClickHandler(event:MouseEvent):void
    {
        if (!tween && visibleColumns && visibleColumns.length > 0)
            super.mouseDoubleClickHandler(event);
    }
    
