Code does not work Firefox 3.

Code does not work Firefox 3.


Hi,
Following simple code does not work on my Firefox 3 and IE (Firefox 2
and Safari are fine).
$.ajax({
    type:"GET",
    url:"file.xml",
    async:false,
    success:function(xml){
         $("tag_in_file", xml).each(function(i){
// do something;
         });
    },
    dataType:"xml",
});
I can see the success handler is call but when it comes to $
("tag_in_file", xml), it does not find it !?
Thanks,
sglai