Not sure what you've done, but I had a hunt round to see what I could change on mine that would control this, and this might be the problem.
Top of the page "My controls" - click on that and on the left is says Menu (Messenger, subscriptions, personal profile etc) - click on "Subscriptions" - click on "View Forums" and change the drop down to unsubscribe.
Might as well do the same for "View Topics" just to make sure that is unsubscribe too.
Did that do it? I have to admit I'd be better if I was sitting looking at your screen rather then guessing what your settings might be, but try this in case it fixes it.
Also, in "options" - "Email settings" you should have two boxes checked - Send me any updates sent by the board administrator and Send a notification email when I receive a new private message.