Why do I keep getting logged out?

[Jeff V]

I log in. Read a thread. Click to reply. Am notified I need to log in again (and sometimes am able to recover my reply going backwards). I was just in a thread, hit the back button to go back to the forum, and was logged out. I'm having to log in multiple times across minutes...it used to be an hour or more before the login timed out.

[Blackhawk]

Could it be a security addon that's deleting the cookie? I only need to log in once every few months, usually after I deliberately clear data.

[Kraken]

Take a hint, dude.

[Rumpy]

Happens a lot to me too. I've tried it both as https and without, and still happens. It's also quite inconsistent. I can have days without it ocurring, other times it can happen several times a day.