ASP.NET MVC 4 : enabling XmlHttpRequest post to controller with $.ajax()

Seems a simple thing but I've spent all day looking through posts all over the web with little recourse! Please help. I have a simple request to be posted to a MVC controller...

 $(document).ready(function () {
    $('#json_request').on("click", function () {
        // send request to server for menu json data
        $.ajax({
            type: "POST", 
            url: location.protocol + "//" + location.host + "/Tablet/Menu",
            data: { restaurantId: $('#restaurantId option:selected').val(), mealSessionId: $('#mealSessionId option:selected').val() },
            success: function (menuData) {alert(menuData); },
            error: function () { alert("failed"); }
        });
    });
});

The request just won't reach the controller! The app works fine when I post the request as a Html form. It works fine with the Visual Studio Development Server too. I get 404 error with IIS 7.0 / ASP.NET / MVC 4. Possibly, contentType: application/x-www-form-urlencoded does not get through the http-protocol filters. Do I have to set those specifically? How? Thanks for your help. I am not send the request as a json, so i did not try contentType: application/json.

Controller / Action:

[HttpPost]
    public ActionResult Menu(short restaurantId, short mealSessionId)
    {
        try
        {
            MenuInput menuInput = new MenuInput(restaurantId, mealSessionId);
            menuInput.LoadMenu();
            if (Request.IsAjaxRequest())
            {
                MemoryStream ms = new MemoryStream();
                menuInput.AsJson(ms);
                string jsonString = Encoding.UTF8.GetString(ms.ToArray());
                JsonResult result = Json(jsonString, "text/x-json");
                ms.Close();
                return result;
            }
            else
            {
                return View("MenuInformation", menuInput);
            }
        }
        catch (Exception ex)
        {
            System.Console.Write(ex.ToString());
            return View();
        }
    }