Problema estrazione dati da file xml

[Vindav]

Ecco un esempio:

Chiamata ajax:

var xmlhttp;
loadXMLDoc();
function loadXMLDoc(){
	if (window.XMLHttpRequest)
  	{// code for IE7+, Firefox, Chrome, Opera, Safari
  		xmlhttp=new XMLHttpRequest();
  	}
  	else
  	{// code for IE6, IE5
  		xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
  	}
	xmlhttp.onreadystatechange=stateChange;
	xmlhttp.open("GET","prova.xml?"+new Date().getTime());
	xmlhttp.send();
}

function stateChange() {
	if (xmlhttp.readyState==4 && xmlhttp.status==200) {
		alert(xmlhttp.responseXML.getElementsByTagName("MATRICOLA")[0].childNodes[0].nodeValue);
	}		
}

xml:

<?xml version="1.0" encoding="ISO8859-1"?>
<ROWSET>
<ROW>
<MATRICOLA>miamatricola</MATRICOLA>
</ROW>
</ROWSET>