I don't know why it's doing it, and not sure how to explain the problem, so please see screenshots

 

log in as this person, sees forum exactly how I want them to

 

then if I log out as that  user, the admin defaults his group to something different

 

then when I log in again as him, the forum has of course opened up to him




How do I stop it from changing his first group?

It's not happening to any other groups??

SOLVED

It never hurts to explain how you solved it, so it might help others who run into similar problems and find/remember this topic. 

I can do that tomorrow.