Cutom AJAX Authencationservice - Invalid web service call, missing value for parameter: 'createCookie'

Hi,
I am getting following Error Message in OnError failedCallback  method of AJAX Authencticationservice
Error Msg : Invalid web service call, missing value for parameter: 'createCookie'.
 
please find the following codes for reference
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Javascrip Files : JScript.js
------------------------------------------------------------------------------------------------------
Type.registerNamespace("JSSK");
JSSK.Membership=function()
{
}
JSSK.Membership.prototype=
{
    BeginLogin:function(uid,pwd,rememberme)
    {
        Sys.Services.AuthenticationService.login(uid,pwd,false,null,null,Function.createDelegate(this,this.EndLogin),Function.createDelegate(this,this.OnE ...