             return;
 
         _orientation = value;
+        _tileWidthCached = _tileHeightCached = NaN;
         invalidateTargetSizeAndDisplayList();
     }
 

    /**
     *  @private
     */
    override protected function elementBoundsAboveScrollRect(scrollRect:Rectangle):Rectangle
    {
        var bounds:Rectangle = new Rectangle();
        // Find the row that spans or is above the scrollRect top edge

    /**
     *  @private
     */
    override protected function getElementBoundsRightOfScrollRect(scrollRect:Rectangle):Rectangle
    {
        var bounds:Rectangle = new Rectangle();
        // Find the column that spans or is to the right of the scrollRect right edge.
