That had been an issue a few months back when we had been under heavy attack by spambots, as they attempted to access the forum by guessing member password. After three failed attempts the forum software will prompt for a password even if the member had actually been on. I'm no sure that is the case here though, but it seems to be happening to others as well. I will try resetting the forum cookie to see if that works. Doing so may require that everyone will be prompted to log in again however.