I've noticed that the sub-forum for real equine is accessable to non-subscribers, but you can't open the different threads.
My suggestion is that if you can't read the threads in the forum, disable that forum altogether for non-subscribers. There's no point in being able to read only the topics and nothing else since it just creates frustration when you see a topic you're really interested in, and when you click it.. wa-wa-waaaa, too bad.. And if not, at least make it like the sale page, non-sub can see topics and read threads, but not post.