，extjs下拉树在IE上出不来！

十万火急，extjs下拉树在IE上出不来！！！
代码如下，在火狐下正常，在IE下点击下拉列表后什么也没有，原因不知，麻烦各位给我看一看哪里的问题

JScript code

var comboxTree = new Ext.form.ComboBox({           store:new Ext.data.SimpleStore({fields:[],data:[[]]}),           editable:false,           mode: 'local',         width:100,        listWidth:220,        triggerAction:'all',        tpl: "<div style='height:300px'><div id='thistree'></div></div>",           selectedClass:'',           onSelect:Ext.emptyFn       });       var tree = new Ext.tree.TreePanel({           root:new Ext.tree.AsyncTreeNode({text: '部门'}),                 width:220,         border:false,            autoScroll:true,         autoHeight:true,         rootVisible:false,          loader: new Ext.tree.TreeLoader({dataUrl:'loadDepartTree?node=0201'})                });         tree.on('click',function(node){             comboxTree.setValue(node.id);             comboxTree.setRawValue(node.text); v             comboxTree.collapse();         });       comboxTree.on('expand',function(){           tree.render('thistree');           tree.expandAll();        comboxTree.ownerCt.doLayout(true);      });         var form = new Ext.form.FormPanel({        region:'center',                                items:[                                  comboxTree               ]                                                                                                       });    var view= new Ext.Viewport({                //hidden:true,                layout:'border',                items:[                                                  form                                                ],                renderTo:Ext.getBody()                                  });        view.show();        

JScript code

Ext.ux.ComboBoxTree = Ext.extend(Ext.form.ComboBox, {    tree: null,    SelectAll: true,    displayText: 'Text',    constructor: function (config) {        var $this = this;        var rid = Math.floor(Math.random() * 1000);        this.tree = new Ext.tree.TreePanel({            loader: config.loader,            border: false,            root: config.root,            rootVisible: config.rootVisible,            autoScroll: false,            listeners: {                click: function (node, e) {                    if ($this.SelectAll) {                        if ($this.displayText == 'Text')                            $this.setValue(node.attributes.name, node.attributes.id);                        else if ($this.displayText == 'Name')                            $this.setValue(node.getPath('name'), node.attributes.id);                        $this.collapse();                    }                    else if (node.attributes.leaf) {                        if ($this.displayText == 'Text')                            $this.setValue(node.attributes.name, node.attributes.id);                        else if ($this.displayText == 'Name')                            $this.setValue(node.getPath('name'), node.attributes.id);                        $this.collapse();                    }                }            }        });        config = Ext.apply({            editable: false,            triggerAction: 'all',            autoScroll: false,            typeAhead: true,            tpl: "<div style='height:200px'><div id='_" + rid + "'></div></div>",            listeners: {                expand: function () {                    this.tree.render('_' + rid);                    //tree.expandAll();                }            }        }, config);        Ext.ux.ComboBoxTree.superclass.constructor.call(this, config);    }})///贴一段我的代码