Simple Q: Subdomain access to visitors

Have 2 levels on a multisite with subdomains, my membership tables are GLOBAL. The 1st level is Visitor. The 2nd is FREE.

The idea for level 1 is the visitor can visit the main blog and i limit access to menu options and pages, He also has no access to any buddypress functionality. This part works of.

Level 2 is FREE, but requires registration - so far it has been working fine. So the FREE level then gives access to the buddypress side of the site (also on main blog), and to further menu options and pages on main site.

NOW >>> the problemo... (yes there MUST always be a problem).... say I have 10 network sites (blogs on subdomains)... using the global tables the new signups appear fine in these blogs users tables... I want to limit the VISITOR level to full access on say BLOG A AND BLOG B.... but if they want access to BLOG THE REST aaah you need to sign up buddy...press the register button....

NOW this part is NOT working. I have in postive rules tried to allow by clicking on the sites i want them to have access to, and tried also the other way, in negative rules to tick the ones they dont have access too, seperately i mean, tried both ways... NO GO

Whatever i do, when they visit the 2 sites in question, the 1st redirects them immediately to sign up, the 2nd does not redirect them but they get 404 errors when trying to access posts....

If i disable membership.... aaaah well then all works

HINTS, clues, ideas?