Due to the slightly weird way that Drupal works, error messages often get delayed until the next page you view after the one that generated the problem. So you could see these errors on any page of the site, if you view that page immediately after visiting one of the troublesome forum posts.
For the time being, I’ve installed a filter which I think should be hiding these errors. The errors are still happening, which isn’t ideal, but I think you shouldn’t see them any longer.