I've noticed lately that when I log in upon reaching the home page and then navigate to a forum page, I have to log in again. This happens even if I click the "remember me" button. Not an earthshaking problem, but a bug y'all might want to fix!
Just wanted to mention that I had a similar problem. Last night (early this morning actually) I was only getting 'guest' access for a while. When I tried to log on, it would accept my username and password but then keep me as a guest. The same thing happened in both Firefox and Internet Explorer (which did not have cached data or cookies for APC). I tried again 20 minutes later and it worked fine, and that's the only time I've had it happen to me.