child blog registration not possible since Buddpress install'n

I installed Buddpress on my multi-site network. Since doing so, new subscribers are unable to register for a specific child blog. They just become subscribers of the main blog, but can't access a dashboard for a child blog like they could before the Buddypress install'n. Is there a solution for this? Did make a mistake? Is this a known consequence of installing BP to a multi-site network blog.