Losing sessions...

I have an application that I have been running under Tomcat 4.0.6. In some JSPs I have regular HTML anchor tags which call servlets in another part of the application < a href="ServletName?oper=add"... In Tomcat 4.0.6 these links work fine and the session persists with these calls.
When I tried the application on a newer version of Tomcat 4.1.24 or 5.0.12 I 'lose'(for lack of a better term) the session when I use this link. I was just curious about this change, if it was a problem with 4.0.6 or the newer versions, and why.
Or, have I missed something in my web.xml or server.xml?
My context in server.xml is pretty much the default, and my web.xml is really just servlets and their mappings.
I have left the Session manager with the default settings and also tried the PersistentManager settings, to no avail.
Thank you.

You should not be "losing" sessions if all servlets and JSP are part of the same web application. I don't think that Tomcat changed anything related to this between 4.0.6 and 4.1.24, but you might want to look at the release notes.
Bill (mystified)

Basically what seems to be happening:
Start at: ServletA - session1 created
Uses the RequestDispatcher forward to go to: ServletB - uses session1
In ServletB there is an exception thrown by my application MyAppException.
This is handled by an error page defined in web.xml, Error.jsp - the error page uses session1
Error.jsp has a link <a href="ServletB">
Follow this link...
ServletB has no session. So in ServletB the code:

creates a new session and

leads to a NullPointerException.

Are either of these servlets addressed using the "invoker" style URL - like /servlet/ServletA
I think it is possible to lose track of a sessionID that way.
I also wonder if the Error.jsp response is sending the sessionID in the response - since thats the only way the client will get the sessionID.
Bill