Ajax Call Failed

hi all,
i have converted a web application from asp.net 2.0 to asp.net4.0. Originally the code behind  [Ajax.AjaxMethod()] methods referring Ajax.dll(which is under bin folder, Run Time Version v1.1.4322).
assume that i have a method in code behind like below
[Ajax.AjaxMethod()]         public DataView GetDet()         {         }
and calling above function from javascript like this
POI.GetDet(ExpandMnetLine_Response);
it was working fine in my old 32 bit server(win 2003).
Now, i pulished the same code into 64 bit Windows 2008 R2 Server there, wherever the AJAX methods are calling those places, it raising javascrip error as "object not defined" etc.,
below is the error message im getting while accessing the Ajax method
The file '/ajax/MyProject.UI.ShowInvPrint,GPM.Web.UI.a ...