Noob: Could not load XML file

Hi all,

I can't seem to access the XML file. When I use a relative path,
request.responseXML gives me false, and I get the alert shown in the
code below. It gives me the same error even when I hardcode the gpx
file: http://www.ecopath.org/NonEwe/test/googleMaps/googleMapGroups.gpx
, (and the file does exist)

I'm a little bit stumpped. Is this a security problem on my server?

// Load and parse GPX file
// Builds .gpx filename based on html file
//
var request = GXmlHttp.create();
URL = document.URL;
URL = URL.replace(/\.html$/,".gpx");
URL = "googleMapGroups.gpx";
request.open("GET", URL, true);

request.onreadystatechange = function() {

if (request.readyState == 4) {
var xmlDoc = request.responseXML;
if( !xmlDoc ) {
alert("Could not load GPX document " + URL);
} else {

Here's the URL
http://www.ecopath.org/NonEwe/test/googleMaps/googleMapGroups.html