Wow, it deja vu all over again. I find that cliques in the workplace are more the rule than the exception these days. My advice is to raise your visibility for sharing info and include your manager. The manager will begin to notice that you are open and willing to share info while the others are closing you out. If the manager is for info-sharing then you'll have his buy-in and he can then encourage an "all for one, one for all" mindset for his team. However, if the manager is setting the tone for the clique by feeding it or choosing to ignore it then he is actually part of the problem, and it may be time for you to move on and find greener pastures when you can.