(from Mathias Scharl)
The ConversationManager uses a DUMMY variable set to new Integer(-1). Later in the code this DUMMY is used to check for an invalid conversation id. Unfortunately this check is done via == instead of equals, which works most of the time, but after re-starting an application in tomcat (session is passivated), the DUMMY object is not the same anymore and the check does not work as expected. The solution is to use equals instead of ==.