//set them to what we need for the parser to behave
XML.ignoreComments = true;
XML.ignoreProcessingInstructions = true;
XML.ignoreWhitespace = true;
XML.prettyPrinting = false;
XML.prettyIndent = false;
//var response = new XML (xhr.responseXML);
var response = new XML (Components.classes['@mozilla.org/xmlextras/xmlserializer;1'].createInstance (Components.interfaces.nsIDOMSerializer).serializeToString(xhr.responseXML.documentElement));