panel viewport missing scrollbar in ie extjs

I've the following Extjs code that works fine in FF but in IE a vertical scrollbar does not appear when overflow happens in west region. Whats wrong?

Ext.onReady(function(){

   var viewport = new Ext.Viewport({
        layout:'border',
        items:[{
            region:'west',
            id:'west-panel',
            split:true,
            width: 250,
            minSize: 175,
           开发者_StackOverflow社区 maxSize: 400,
            collapsible: false,
            margins:'5 0 5 5',
            cmargins:'5 5 5 5',
    border: false,
            autoScroll:true,
    layout:'fit',
            layoutConfig:{
        autoWidth:false
            },
            contentEl:layers
        },{
            region:'center',
            margins:'5 5 5 0',
            layout:'column',
            autoScroll:false,
    border: false,
            contentEl:main
            }]
    });

});

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I did try the above code now and here seems to be no problem at all for IE8,FF& chrome. Which version of IE are you using? Also, what are the values inside the layers and main? I just put 'Lorem ipsum' text seems to work fine for me!