         if (value > _numColumns)
         {
             for (var i:int = value - _numColumns; i < value; i++)
-                cellHeights[i] = 0;
+                cellHeights[i] = -1;
         }
         else
         {

        }
        
        const changed:Boolean = maxCellHeight != max;
        maxCellHeight = max;
        return changed;
    }
    

        this.rowIndex = rowIndex;
        _numColumns = numColumns;
        
        // initialize cellHeights. all are -1 to start out with.
        cellHeights = new Vector.<Number>(numColumns);
        GridDimensions.clearVector(cellHeights, -1);
    }
    
    private var _numColumns:uint;
