I had an issue today of it logging me out when I accessed the board index. I have Firefox remember my log in/password and remember me checked. Could've been when they were working on the phone lines in front of my house this afternoon though.
I've had IPB look into this and they made a few slight adjustments to help those affected. All those who are affected should to ensure they clear their browser cache or at a minimum hard refresh (CTRL+F5 on a Windows machine) their browser on your board index page, then login if necessary. Hopefully they will stay logged in now.
Yeah, it happened to me again today. I was logged in earlier this afternoon, browsed other places and came back here to find that I had to log in, again.