I am using Ext JS to make a popup window, here is the code:
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");
}
In firefox this works fine. In IE7 it works, but always produces a javascript error saying "unspecified error".
What am I doing wrong?
EDIT
Removing the anchorTo line removes the error. I would still like to anchor to though so this isn't a great solution!