Ajax query no works in IE6

This is the code:

$(function(){
$.ajax({
       url: "config_es.xml",
       success: function(data,textstatus,resquest){
             var xml = resquest.responseXML; }
       });
});

I am using the object xml to get information of the config file(config_es.xml). This works right in Firefox, Chrome, but not in IE6. I dont know what is the problem. I have not tested it in IE7, neither in IE8.