I have a new MacBook Air set up with FileVault.
In the Security Preference pane I have "Require password 1 hour after sleep or screen saver begins" enabled, but the "Logout after 60 minutes of inactivity" is disabled.
When I leave the computer on overnight I manually lock the screen (from the Keychain status menu bar, which I enabled via the Keychain Access preferences).
Alas, in the morning I find that instead of a locked screen I see the login window, after my user was logged out with all applications terminated... (e.g. Firefox thinks it previously crashed when I launch it).
This type of behavior only started after I enabled FileVault.
Why is this happening? How do I prevent such auto-logout?