The main index was showing there were new posts in the 'Help' board. Click on the board, and no new posts were highlighted, but the new post was there, although the thread containing the new (latest) post was not at the top of the ladder. Tried it several times - the same. Eventually clicked on 'Mark as read', and got a session error. Had to close down and restart CA. I'm on XP, IE8.
hmm - I can't see the problem. Next time it happens, try closing IE, clean out cache and all cookies (or at least all ClubArnage ones) and restart IE, and see if that changes things.
/Djet