Is your login session expiring because you set it to a short time when you first login? I set mine to forever and then after flushing my history, close Chrome & reboot my Win7 machine frequently. So I've never had my session get a chance to expire which theoretically could happen between reading and posting.
You didn't give us any OS or browser info so this may not apply. Back when using WinXp and IE, I'd get issues with login credentials not clearing/resetting IF I had a Windows Explorer window open in the background. After learning to close those windows before closing out of a session and closing IE so I could start a fresh session under another ID, I stopped having issues. IE was set to clear the history on closing and I had the settings configured to not store login info so that I shouldn't have had issues but somehow Windows Explorer seemed to keep the previous session info live. Thanks Micro$oft!
If you haven't done so in a while, you might try purging temp files & login data, closing browser and explorer windows and see if a reboot works. As a software tester, I do it habitually and frequently which helps me avoid oddball browser behavior.
