Same here now, Firefox on Win 8.1, Account Button is only showing on the front page, on the forums pages it's just a blank white spot. Before it often displayed "Sign In/Log In" instead of "Account", even though I was already logged in and also able to post. It wasn't persistent though, sometimes, after a while or after shutting down the browser (thereby clearing cache and cookies) and then logging in again, it was back to normal. I also noticed occasional delay regarding the message notifications. I'd check my replies, but the notifications kept on being displayed, even though when I went to "Messages" or "Forum Replies" again, there were none.