LJ seems to have a gift for expiring your login just before you attempt to post. It's really frustrating. And just now, having decided that I could view a locked post (still logged in), but not reply to it (sorry, not logged in), it challenged me with an anti-spam text-as-image. I wouldn't mind, but the same window also offered logging in, so I chose that instead, Nope. Seems you have to respond to the challenge anyway. Sigh.