ajax method is not called after the first invoking at IE

ajax method is not called after the first invoking at IE

   $("#test").droppable({
     tolerance:'touch',   
       drop: function() { 
$(this).find("table > tbody").append(newRow); 
       $.ajax({ url: "myUrl"});
       }
    });

The above code works fine at Firefox and Google Chrome. And it works at IE 8 for the first drop action. The ajax method is not called after the first call although the append still works.

Is a beg with jQuery or usage issue?