There are two methods GetUserAssignedSystems() and GetUserAssignedSystems(string Id) These methods act very differently from each other. The problem is, when I want to call GetUserAssignedSystems(string Id), the parameter-less method is called.

Here are the methods:

[WebMethod]
    [ScriptMethod]
    public IEnumerable GetUserAssignedSystems(string cacId)
    {
        return Data.UserManager.GetUserAssingedSystems(cacId);
    }

[WebMethod]
    [ScriptMethod]
    public IEnumerable GetUserAssignedSystems()
    {
        //do something else
    }

Here is the jquery making the call:

CallMfttService("ServiceLayer/UserManager.asmx/GetUserAssignedSystems", "{'cacId':'" + $('#EditUserCacId').val() + "'}", function(result) {
        for (var userSystem in result.d) {
            $('input[UserSystemID=' + result.d[userSystem] + ']').attr('checked', 'true');
        }
    });

Any ideas why this method is being ignored?