BuddyPress.org

Is it possible that your host automatically re-routes subdomains for you, rather than allowing them via a wildcard? Or that your .htaccess file is bouncing things back?

I’ve seen some installations where if the server wasn’t configured for subdomains, that the subdomain was put through the URL as a _GET or _POST variable.

When you create a new user/blog, does the blog actually get created? If so, can you navigate to ANY blogs or do all of them bounce back like that?