I was having that problem, but I finally broke down and cleared out all temp internet files and cookies, and all was better. It was strange, because this was the only message board (of many that I go to) that was acting up. It'* working correctly now, though. So I would suggest that as a possible fix for you.
Be advised, that any other sites that you visit, you will need to log in to those again, to get re-cookied (or whatever the technical word is).