Hi, The setup: -Zope 2.2.4 -Core Session Tracking 0.7 -Cookie session ID manager (path=/,lifetime=0) -Internal Session Data Manager (timeout set to 60 minutes) This seems to randomly (but sometimes very frequently) loose session data items :-( I've sprayed lots of log statements around (including in SessionData.invalidate, to ensure I wasn't inadvertently calling it) and so far it appears that the session id cookie is being returned by the browser (so path, lifetime, etc are probably okay) but self.session.getSessionData().get('Type','') is often returning an empty string, even when I know it has been set. This is an intermittent problem though, so it's probably going to be a bitch to track down :-( There's doesn't seem to be any correlation with the 'Can't Load State for x' problem I reported earlier, but I guess it could be the same thing. Anyway, please help, I'm loosing (hair|sleep|etc) over this :-( cheers, Chris