win close不了？

if(user_From.form.isValid())
                            {
                              
                                user_From.form.submit(
                                  {
                                    url:'user_exec.jsp?operate=ADD',
                                    method:'get',
                                    params : '',
                                    waitMsg : '正在保存数据，稍后...',
                                    success : function(re,v){            
                                      var jsonobject = Ext.util.JSON.decode(v.response.responseText);  
                                      if(jsonobject.success=='true'){
                                        Ext.Msg.alert("添加用户",jsonobject.msg);
                                        win.close();//关闭不了,好奇怪啊
                                      }                                    },
                                    failure : function(re,v) {
                                        var jsonobject = Ext.util.JSON.decode(v.response.responseText);
                                        Ext.Msg.alert('添加用户',jsonobject.msg);
                                    }                                  });
                                                              }