Ajax problems while using by dll

Question

I am using asp.net 3.5, and Ajax.dll in my application.

I used ajax.dll, to load a list of itmes, with search options.

After keeping my page as idle for one hour if i click anything which could cause javascript error, its not working, it says {ClassName} is undefined.

Let me explain it,

I have registered a Ajax method,

Utility.RegisterTypeForAjax(typeof(Default)); in page load.

I am trying to get the values from the server

like

*[Ajax.AjaxMethod(HttpSessionStateRequirement.ReadWrite)] public string GetNames() {

return "Ramesh" ; }* from javascript i am accessing the method by calling

var Data=Default.GetNames().value;

sometimes it throws Default is undefined.

Can someone please look at this issue?