That system is supposed to change, but it happens to me sometimes also. I think it might have to do with clearing the cache, and sometimes you have to sign on twice...once on the home page and again on forums. If you didn't do the latter and navigate to the galleries, you won't be signed in.
Also...don't tell anyone I let on, but the comment section in the galleries has been really glitchy lately, with double posts. Maybe you've been experiencing another of the glitches.
