 			var obj:Object = itemRenderer;
             if (isNaN(explicitRowHeight))
             {
-                if (iterator && columns.length > 0)
+                if (iterator && _columns.length > 0)
                 {
                     if (!measuringObjects)
                         measuringObjects = new Dictionary(false);


        var o:EdgeMetrics = viewMetrics;

        var n:int = columns.length;
        if (n == 0)
        {
            measuredWidth = DEFAULT_MEASURED_WIDTH;

        var columnMinWidths:Number = 0;
        for (var i:int = 0; i < n; i++)
        {
            if (_columns[i].visible)
            {
                columnWidths += _columns[i].preferredWidth;
                if (isNaN(_minColumnWidth))
                    columnMinWidths += _columns[i].minWidth;
            }
        }

