You document has no Doctype, no HTML, no HEAD and no BODY. Some of them, in different conditions, are not required, but all of them, in your case, might bring errors. The Doctype is a must.
swfobject is not defined
handler is undefined
document.getElementById("curtains") is null
Regarding the XML, you have some empty tags <SPOTIFY></SPOTIFY>. It looks like IE consider them as absolutely empty, thus without any textNode which could be the childNodes
you may try
x[i].getElementsByTagName('SPOTIFY').textContent || x[i].getElementsByTagName('SPOTIFY').text