JSP Session populated with class not working after redirect

Question

Hi,
I create a session (code sample 1 below) on my index.jsp page. Index.jsp has a form on it, and a button that points back to index.jsp. The page is dynamically generated.
The session is created fine, and persists properly between pages.
However, on the last page, i re-direct the user to summary.jsp (with code sample 2), and on that last page (using the session CODE SAMPLE 3) i get an error.
Internal error: servlet service function had thrown ServletException (uri=/imac2/summary.jsp): javax.servlet.ServletException: jsps.imac2._index_jsp$userSession, stack: javax.servlet.ServletException: jsps.imac2._index_jsp$userSession at jsps.imac2._summary_jsp._jspService(_summary_jsp.java:681) , root cause: java.lang.ClassCastException: jsps.imac2._index_jsp$userSession at jsps.imac2._summary_jsp._jspService(_summary_jsp.java:611)
How can I resolve this. The userSession class is defined simply as
public class userSession
Code Sample 1 ########################
userSession requestData;
if (session.isNew())
     requestData = new userSession();
     session.setAttribute("sessionRequestData", requestData);
     %>NEW SESSION <%
}else
     if (QuestionID == 1)
          requestData = new userSession();     
          session.invalidate();
          session = request.getSession(true);
          session.setAttribute("sessionRequestData", requestData);
          %>STALE SESSION, RECREATED<%
     }else
          if (session.getAttribute("sessionRequestData") == null)
               requestData = new userSession();
               %>WONKY SESSION<%     
          }else
               requestData = (userSession)(session.getAttribute("sessionRequestData"));
               %>STALE SESSION<%
CODE SAMPLE 2 ##################
response.sendRedirect(response.encodeRedirectURL(myPage.getPage() + "?path=" + Path + getDataPass(request)));
CODE SAMPLE 3 ##################
if (session.isNew())
     requestData = new userSession();
     session.setAttribute("sessionRequestData", requestData);
     %>NEW SESSION <%
}else
     if (session.getAttribute("sessionRequestData") == null)
          requestData = new userSession();
          %>WONKY SESSION<%     
     }else
          requestData = (userSession)(session.getAttribute("sessionRequestData"));
          %>STALE SESSION<%
}

Answer 1

Further Information:
Swapping out the code in summary.jsp to be
     userSession requestData;
     Object o = session.getAttribute("sessionRequestData");
     if (o == null)      {
               %>NULL <%
     }else
               %>ELSE<%
     if(o!=null) { if (o instanceof userSession) out.println("yey"); else out.println("nei"); }
returns: ELSEnei
So its there, its not null, and its not my object... Why?