InfoPath Dev

I am having an issue while maintaining Sessions in Web Services and Infopath.

This is a test web method to set session values

[WebMethod(EnableSession = true)]
        public void Setvalue()
        {
              Session["groupID"] = 123456;          
        }

 [WebMethod(EnableSession = true)]
        public Int64 Getvalue()
        {
            return Convert.ToInt64(Session["groupID"]);
        }

I am using a Web Service Application project to run this. It works fine when I run the application from .Net IDE. But when I try to browse it from ITENMGR or call the same web Method from Infopath it gives me an error of "Object ref not set to an instance of an object". I even tried to publish the web application but it does not work for me.
I tried to investigate this further and found that it the breakpoint does not stops at Session_Start and Application_Start in Global.asax file while browsing the service from INETMGR meaning the session object is not initialized. On the other hand when I run the application from .NET IDE, breakpoint hits the Session_Start function in Global.asax.

I know this is wierd but please guide me if I am doing some thing wrong.

 I got it this is because of WSS 3.0. My virtual directory which calls the web service is under SharePoint - 80. Therefore it overwrites the setting in Web service project. When I try to create a new virtual directory under Default Web Site it works fine.

Do anyone know how can I configure WSS 3.0  SharePoint - 80 to enable sessions.