I recently updated to 4.1 from 3.x.   Everything is working really well and our members love the new forum.

There are a number of members where the forum seems to continuously log them out even if they check off the Keep Me Logged in checkbox on login.

It happens to me on occasion too where I will get kicked out of my session and have to login again.  This never used to happen on the old board.

Anyone have any ideas of what might cause this?

Cookie Settings ? Are you running Varnish Cache ?

I've had a few members report the same thing. I've noticed it myself as well. Using memcached, nginxcp, and fcgid. It's intermittent and not affecting all my users. Very strange.