"Argumento no valido" en IE

[poroto20]

Va el resto del codigo, la respuesta del llamado de Ajax es correcta (eso lo verifiqué)

Código:

function loadNotes(id,notes,edit){
var url = './../../../users/notes/?photoId='+id+'&type=load';
var ajax = new Ajax.Request(url, { 
						method: 'get' ,
						asynchronous: true,
						onComplete: showResponse});
	
function showResponse(xmlHttpRequest, responseHeader){		
	var xmlMessage = xmlHttpRequest.responseXML;
	alert(xmlMessage);
	var records = xmlMessage.getElementsByTagName('note');
        for(i = 0; i < records.length; i++){
               var text = getNodeValue(records[i],'text');
              var w = getNodeValue(records[i],'width');
              var h = getNodeValue(records[i],'height');
              var top = getNodeValue(records[i],'top');
              var left = getNodeValue(records[i],'left');
              var iddb = getNodeValue(records[i],'iddb');
              var note1 = new PhotoNote(text,3,new PhotoNoteRect( left,top,w,h));
              note1.iddb = iddb;
              note1.editable = edit;
              note1.onsave = function (note) { ajaxreq(note,id); return 1; };
               note1.ondelete = function (note) { ajaxreqdelete(note,id); return true; };
			notes.AddNote(note1);
		}
	}
}


function getNodeValue(obj,tag)
{
	return obj.getElementsByTagName(tag)[0].firstChild.nodeValue;
}