Due to a bug in the software, subscribing to certain topics or subforums is not working properly. Therefore, the option to subscribe has been discabled for now. As soon as a bugfix becomes available teh feature will be tested and if it works, subscribing will be enabled again.
Meanwhile, check back once in a while - a little red star in the topic icon shows activity in a topic since your last visit (if you're logged on, of course).
Frank>