十万火急，extjs下拉树在IE上出不来！！！

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();