It may be as simple as your web browser caching the pages. Since it caches before you are logged in, after a post the page is built from whats already on your pc (thus the login boxes up top and no name in the list) if you hit refresh or reload then you should see if you're truly logged out or not.
If you set the autologin to be active, you should never be logged out. Works great and is less filling... [=)]
Seriously, I recommend setting your caching value to "Every Vist To Page" (so the dynamic content is loaded every click), this may be a bit slower for modem users, but at least you will see whats going on without having to hit refresh.
(If you're not accepting cookie, you will be logged off as well, session timeout is 15mins and session cookies are used to track who you are and that you're logged in.)
-- GB