First of all to point out that I m begginer with javascript and web services. Some days now i try to make out how does $.ajax works but I face some problems... I have get a lot of help till now from forums but still i have some questions...
I have include lib Json2.js
and i use IE 7
Here is my code

var objuser ={"companycode": "test1"," usercode": "test2","applicationname":"test3"};
    type: "POST",
   url: "localhost:51136/Service2.wsdl/FindByUserAndApplication",
   contentType: "application/json; charset=utf-8",
   //data: objuser, i tried this also but i got the same error 
   datatype: "json",
   success: function (msg) {
    error: function(req, status, error) {
        alert(req + ", " + status + ", " + error);
    } ,
    complete: function(req, status) {
               alert(req + ", " + status);

as response i get the a web page message : "NaN [Object error]"
Do you have any idea what this means??? Or how to fix it???

I tried also to call a more simple service which displays just a "Hello world"
but i got the same error again.

I have searched a lot but I cannot figure out what I do wrong...

Thank you a lot in advance