How to work with treecombo in Extjs 4.1

I found tutor in http://www.sencha.com/forum/showthread.php?198856-Ext.ux.TreeCombo
I try to make a treecombo in Extjs4.1 in http://jsfiddle.net/rq2ha/ here is my code

Ext.onReady(function() {
        Ext.create('Ext.ux.TreeCombo', {
            margin:10,
            width:120,
            height: 10,
            treeHeight: 10,
            treeWidth: 240,
            renderTo: 'treecombo3',
            store: storeMenu,
            selectChildren: false,
            canSelectFolders: true
            ,itemTreeClick: function(view, record, item, index, e, eOpts, treeCombo)
            { 
                var id = record.data.id;
                // I want to do something here. 
                // But combo do nothing (not selected item or not finish) when i init itemTreeClick function
            }
        });
});

1st problem: I want to get id of tree and do something When i click item of tree on combo. But combo not complete (seleted) when i click (combo do nothing).

2nd problem: if i change store is dynamic like

var treestore = Ext.create('Ext.data.TreeStore', {
        proxy: {
            type: 'ajax',
            url: 'example.php',
            reader: {
                type: 'json'
            }
        },
        autoload: true
    });

I will get error

my json

[ { id : '1' , text : 'a', iconCls: 'cls1' ,children :[{ id : '2' , text : 'b', iconCls: 'cls2' ,children :[{ id : '9' , text : 'a', iconCls: 'cls' ,children :[]},{ id : '14' , text : 'a', iconCls: 'c' ,children :[{ id : '33' , text : 'b', iconCls: 'cls' ,children :[{ id : '35' , text : 'a', iconCls: 'cls' ,children :[{ id : '36' , text : 'a', iconCls: 'cls' ,children :[]}]}]}]},{ id : '16' , text : 'd', iconCls: 'cls' ,leaf:true}]},...

How can i fix that thank