Xubuntu 11.04, on a Compaq laptop, running Compiz. 

My session is automatically saved at logout even it is not asked for. 
Even if:

-the case "save session automatically at logout" is unchecked in "settings manager, session and startup, principal".
-I have saved a specific session in "settings manager, session and startup, session". The last session is written over. 
-I have deleted the content of /home/<user>/.cache/sessions  
=>the last session is always written over and the applications running at logout are launched at startup. (Note for another bug: skype behaves buggy in this case, the tray icon randomly disappears)


I found a (cheap) workaround: after saving your base session, set Read only permissions to /home/<user>/.cache/sessions and his content recursively. It works seamlessly for me.