Keeping Session Values !

In one JSP page , I have declared a session variable as -->
session.setAttribute("S_USERID",strUserId);
where strUserId is a STRING variable with some value .
If I get the Session variable in the same page using -->
String strUsr = (String)session.getAttribute("S_USERID")
the value is retrieved , but if I use the same Syntax in the next JSP Page where the control goes , the value retrieved is NULL .
I have also used the following tag in the next JSP Page -->
<%@ page session="true" %>
I have even checked the Session Ids in both the pages , they are the same.
Can u tell me why it is happening ?
I am using iPLanet Application Server . Do I need to set some parameters while deploying ?
Also suggest me a possible solution .

As far as I am concerned it should work.
are u giving this code at the begining of each page
<%@ page language="java" session="true" %>
I suppose try changing the server.
I am using resin server..quite good..infact tomcat had given me some problem..but this is a very user friendly server.
hope this helps