The early symptoms of a team breaking down are subtle - not unlike cracks in a dam. It usually starts with erosion in Trust which shows up in communication break downs, seeking out who to blame, looking out for #1 or being too busy to help each other out.

What I look for is when someone comes to me as the Leader looking to share information about another team mate. If the information gets their team mate "out of trouble" they're working as a team; if the information gets their team mate "in to trouble" then the dam is starting to break.