The new posts indicator is meant to show you the forums that contain posts that were added since your last browser session. A browser session encompasses the time the web browser is opened to the time it is closed.
The problem that I am referring to manifests itself such that the new posts indicator does not reset after each browser session.
If you're having trouble with the new posts indicators when viewing the message board with the Firefox web browser try the following link http://www.mytoos.com/cgi-bin/ultimatebb.cgi?ubb=markallread
Note that a browser session ends when all instances of the browser have closed.