Sobreescibir remote: de Jquery.validate

1.js

// http://forum.jquery.com/topic/validate-using-remote-webservice-and-json-not-working

$(".fieldUsername").rules("add", {                                              
                  remote: function(){
                                      var r={
                                             type: "POST",
                                             url: "/wservices/clientscriptservices.asmx/CheckUserNameExist",
                                             contentType: "application/json; charset=utf-8",
                                             dataType: "json",
                                             data: "{'username':'" + $(".fieldUsername").val() + "'}"                       
                                      }
                                      return r;
                                    }
                                               
});