      */
     public function insertColumns(startColumn:int, count:int):void
     {
-        GridDimensions.insertValueToVector(cellHeights, startColumn, count, 0);
+        GridDimensions.insertValueToVector(cellHeights, startColumn, count, -1);
     }
     
     /**

     */
    private function updateMaxHeight():Boolean
    {
        var max:Number = 0;
        for each (var cellHeight:Number in cellHeights)
        {
            if (cellHeight > max)

     */
    public function clearColumns(startColumn:int, count:int):void
    {
        GridDimensions.clearVector(cellHeights, -1, startColumn, count);
        updateMaxHeight();
    }
    
