Google Maps y XML

[Sidreru]

Wenas

Estoy probando a integar Google Maps con un archivos XMl de direcciones siguiendo un tutorial propio de Google ( http://code.google.com/support/bin/a...22&topic=11369 ).El problema es que al intentar leer el XMl me sale un error "documentElement es nulo o no es un objeto". El codigo que tengo es este:

Código:

<script type="text/javascript">
    //<![CDATA[

    var iconBlue = new GIcon(); 
    iconBlue.image = 'http://labs.google.com/ridefinder/images/mm_20_blue.png';
    iconBlue.shadow = 'http://labs.google.com/ridefinder/images/mm_20_shadow.png';
    iconBlue.iconSize = new GSize(12, 20);
    iconBlue.shadowSize = new GSize(22, 20);
    iconBlue.iconAnchor = new GPoint(6, 20);
    iconBlue.infoWindowAnchor = new GPoint(5, 1);

    var iconRed = new GIcon(); 
    iconRed.image = 'http://labs.google.com/ridefinder/images/mm_20_red.png';
    iconRed.shadow = 'http://labs.google.com/ridefinder/images/mm_20_shadow.png';
    iconRed.iconSize = new GSize(12, 20);
    iconRed.shadowSize = new GSize(22, 20);
    iconRed.iconAnchor = new GPoint(6, 20);
    iconRed.infoWindowAnchor = new GPoint(5, 1);

    var customIcons = [];
    customIcons["restaurant"] = iconBlue;
    customIcons["bar"] = iconRed;

    function load() {
      if (GBrowserIsCompatible()) {
        var map = new GMap2(document.getElementById("map"));
        map.addControl(new GSmallMapControl());
        map.addControl(new GMapTypeControl());
        map.setCenter(new GLatLng(47.614495, -122.341861), 13);

        GDownloadUrl("data.xml", function(data) {
          var xml = GXml.parse(data);
          var markers = xml.documentElement.getElementsByTagName("marker");
          for (var i = 0; i < markers.length; i++) {
            var name = markers[i].getAttribute("name");
            var address = markers[i].getAttribute("address");
            var type = markers[i].getAttribute("type");
            var point = new GLatLng(parseFloat(markers[i].getAttribute("lat")),
                                    parseFloat(markers[i].getAttribute("lng")));
            var marker = createMarker(point, name, address, type);
            map.addOverlay(marker);
          }
        });
      }
    }

    function createMarker(point, name, address, type) {
      var marker = new GMarker(point, customIcons[type]);
      var html = "<b>" + name + "</b> <br/>" + address;
      GEvent.addListener(marker, 'click', function() {
        marker.openInfoWindowHtml(html);
      });
      return marker;
    }
    //]]>
  </script>

El XML tiene este formato:

Código:

<markers>
  <marker name="Casa" address="" lat="43" lng="-5" type="" /> 
  </markers>

Alguna idea?

Gracias