WordPress MU

I have 3 membership sites in sub-directories: business, real-estate, and vipmember
http://interactive-media-network.com/reviews/business/wp-login.php?action=register

When I try or a new user tries to sign up it redirects back to http://interactive-media-network.com/reviews/wp-login.php?action=register

bypassing the sub-directories. Does anyone know what would need to be changed in the wpmu script to allow a new user to signup themselves without the admin having to do it manually?
This used to work in earlier versions of mu.

Thank you for your help.

maybe in way earlier version. It hasn't worked like that for a while now.

Users have to register at the main site, then get added to the other site.