[John James Jacoby]

Have you created a page in your root MU blog called “forum” by chance? Also, it kind of sucks but because bbPress pretty permalinks use “forum” to tell the URL that you’re clicking a forum, having your URL be domain.com/forum/forum/name-of-forum is the reason why most people install bbPress in “/forums/” or something else like “/support/” or “/discussion/”

What I’m saying is that it might just be that bbPress or WordPress are getting tripped up on what the redirect is, and maybe conflicting somehow?