ExtJs4 Store加载数据的怪异问题

//这是我的基础BaseStore
Ext.define("Base.store.BaseStore",{
	extend: "Ext.data.Store",proxy: {
	    type: 'ajax',reader: {
	        type: 'json',root: 'data',idProperty: "id",successproperty: "success",messageProperty: "msg",totalProperty: "total"
	    }
	},sorters: [{
        property: 'id',direction: 'DESC'
    }]
});

//第一个model
Ext.define("Script.model.system.SystemMenuModel",{
	extend: 'Ext.data.Model',fields: ["id","name","icon1","icon2","fatherId","modelClass","children"]
});


//第二个model
Ext.define("Script.model.system.SystemRoleModel","roleName"]
});

//俩个sotre
Ext.define("Script.store.system.SystemMenuStore",{
	extend: "Base.store.BaseStore",model: 'Script.model.system.SystemMenuModel'
});

Ext.define("Script.store.system.SystemRoleStore",model: 'Script.model.system.SystemRoleModel'
});

Ext.define("Script.view.system.SystemRoleGird",{
	
	extend: 'Ext.grid.Panel',store: null,columns: [
	          { text: 'id',dataIndex: 'id'},{ text: 'roleName',dataIndex: 'roleName',flex: 1  }
	      ]
});

//问题的关键就在这了,如果不创建store1 ，则表格可以正确绑定数据,如果create了sotre1就不能绑定数据,但数据可以从服务器端正确返回都没问题 就是帮不上，百思不得其解
			var store1 = Ext.create('Script.store.system.SystemMenuStore');
			
			var store2 = Ext.create("Script.store.system.SystemRoleStore");
			store2.proxy.url = "systemRoleController.do?method=queryRoleList";
			
			Ext.create("Script.view.system.SystemRoleGird",{
				store: store2,renderTo : Ext.getBody()
			});
			store2.load();

//但是如果在SystemMenuStore与SystemRoleStore中定义自己的proxy也就是不用继承BaseStore的proxy就好使 真不知道为什么了