Re: 404 /blog /members etc… RC2 WPMU 2.7.1
Since Donncha’s WordPress MU Domain Mapping plugin (aka the sunrise domain plugin) allows you to map a blog to another domain, this could be the issue. I would post on the WPMU forum or, better yet, contact Donncha directly to ask for his assistance. http://ocaoimh.ie/wordpress-mu-domain-mapping/
This is beyond scope of the BuddyPress support forums.