I also have a problem with my Firefox, but only on one of the CPUs I'm using. It logs me out each time I close the browser window. But since it happens only on of of my CPUs, it's not the forum problem. Also, when I access those sites on other browsers, everything's fine.
Does FF log you out on other sites that you want to be remembered at?
All the other sites I ask FF to remember me on(several), it does, no problemo. I reckon it's a problem with the site. Maybe it just doesn't like me...