IE7 Ext JS problem: Unspecified JS error on window.close()

function popupImage(term, imageNumber){

    if(currentPopupWindow!=null){
        currentPopupWindow.close();
    }

    currentPopupWindow = new Ext.Window({
                layout      : 'fit',
                closeAction :'hide',
                plain       : true,
                constrain   : true,
                width: 300,
                border: false,
                html: "Blah blah content"<span onclick="currentPopupWindow.close();">cerrar</span>"
            });



    currentPopupWindow.show(false, function(){
        var el = Ext.get("termimage");
        currentPopupWindow.setWidth(el.getWidth(true)+150);
    });

    currentPopupWindow.anchorTo(Ext.get("dictionarycontainer"), "tl");
}

currentPopupWindow.render(document.body);
    currentPopupWindow.alignTo(diccon, "tl", [40, 80]);

                currentPopupWindow.show(false, function() {
            var el = Ext.get(termim);
            currentPopupWindow.setWidth(el.getWidth(true)+150);
        });