[mediaman]

There also exists the possibility that they were assholes -- most good businesspeople I know are good about letting the new person in.

But in that case given they were who they were, one tactic if you see your friend there is to walk up next to him, loudly say hello and shake hands with him (which opens a crack in the circle as he turns), and then turn to the guy to the left of him, extend your hand, and introduce yourself -- which will force him to open up to you, breaking the circle on the right and left. Then you can do the introductions proceeding from that guy back around the circle up to your friend.