Buddypress with Multisite

Hi,

I've got Buddypress installed on my ProSites multi site installation and when somebody tries to activate it they are getting: "You do not have sufficient permissions to access this page."

How do I sort this so that people can have Buddypress on my ProSites, (all the other plugins work fine and they are installed and configured the same way).

Highest regards,

Holmey