ActionScript3, dropping on stage not working after using MouseEnabled - actionscript-3

Question

I'm trying to do do a BattleShip Flash game using ActionScript 3.
1- I draw a grid (class: com.Battleship.grid) using a gridCell:movieClip (class: com.battleship.GridCell)
2- I draw a ship (class: com.battleship.Bateau)
My objective is when I drag the ship to the grid the alpha cell under the mouse changes, and if I drop:
1- if the droptarget is a gridCell, the ship takes place (works fine)
2- if the droptarget is stage, the ship return to originPosition (not working)
My problem: after I used MouseEnabled= false, the ship can drop on the grid, but not on the stage and still dragging.
Here is my code:
var grid:Grid = new Grid(10,new Point(20,20));
var b1:Bateau = new Bateau();
b1.x = 490;
b1.y = 300;
b1.originPos = new Point(b1.x,b1.y);
addChild(b1)
addChild(grid);
package com.battleship {
import flash.display.MovieClip;
import flash.events.MouseEvent;
import flash.geom.Point;
import flash.events.Event;
public class Bateau extends MovieClip {
private var _originPos:Point;
public function Bateau() {
originPos = new Point();
buttonMode = true;
addEventListener(MouseEvent.MOUSE_DOWN, onDrag);
}
protected function onDrag(e:MouseEvent):void
{
e.currentTarget.parent.addChild(e.currentTarget);
e.currentTarget.startDrag();
e.currentTarget.mouseEnabled = false;
//e.currentTarget.mouseChildren = false;
addEventListener(MouseEvent.MOUSE_UP, onDrop);
parent.addEventListener(MouseEvent.MOUSE_UP, onDrop);
}
protected function onDrop(e:MouseEvent):void
{
e.currentTarget.mouseEnabled = true;
e.currentTarget.mouseChildren = true;
e.currentTarget.stopDrag();
if(dropTarget == null){
x = originPos.x;
y = originPos.y;
}else{
trace(e.currentTarget.name);
if(dropTarget.parent is GridCell)
{
x = dropTarget.parent.x+20;
y = dropTarget.parent.y;
}
}
}
public function get originPos():Point
{
return _originPos;
}
public function set originPos(originPos:Point):void
{
_originPos = originPos;
}
}
}
package com.battleship {
import flash.display.MovieClip;
import flash.events.MouseEvent;
public class GridCell extends MovieClip {
private var _row:int;
private var _col:int;
private var _val:int;
public function GridCell()
{
addEventListener(MouseEvent.CLICK,onClick);
addEventListener(MouseEvent.MOUSE_OVER,onMouseOver);
addEventListener(MouseEvent.MOUSE_OUT,onMouseOut);
}
public function onClick(e:MouseEvent)
{
//trace("(" + e.currentTarget.row+ ", " + e.currentTarget.col + ")");
trace(e.currentTarget.name);
}
public function onMouseOver(e:MouseEvent)
{
alpha = 0.6;
}
public function onMouseOut(e:MouseEvent)
{
alpha = 1;
}
public function get row():int
{
return _row;
}
public function set row(row:int):void
{
_row = row;
}
public function get col():int
{
return _col;
}
public function set col(col:int):void
{
_col = col;
}
public function get val():int
{
return _val;
}
public function set val(val:int):void
{
_val = val;
}
}
}
package com.battleship {
import flash.geom.Point;
import flash.display.Sprite;
import flash.events.MouseEvent;
public class Grid extends Sprite {
private var _size:int;
private var _position:Point;
public function Grid(size:int,position:Point):void
{
_size = size;
_position = position;
var gridCells:Array = new Array(size,size);
var i,j:int;
for(i=0;i<size;i++)
{
gridCells[i] = new Array();
for(j=0;j<size;j++)
{
var cell:GridCell = new GridCell();
cell.row = j+1;
cell.col = i+1;
cell.x = this.position.x + cell.width * (i+1);
cell.y = this.position.x + cell.height * (j+1);
cell.name = "cell" + (j+1) + (i+1);
//cell.addEventListener(MouseEvent.CLICK,onClick);
gridCells[i][j] = cell;
this.addChild(gridCells[i][j]);
}
}
}
public function get size():int
{
return _size;
}
public function set size(size:int):void
{
_size = size;
}
public function get position():Point
{
return _position;
}
public function set position(position:Point):void
{
_position = position;
}
}
}