One of the risks to a project's success is a dysfunctional team. It's common for team morale to fluctuate as a project moves through its life cycle - project politics, bureaucracy, challenging overtime demands, etc, can all take their toll on a team. A team under stress can take a couple of diverging roads - from what I've experienced a team can rise to the challenge (like a family) and grow stronger, or digress into a winner-takes-all environment (like Survivor).

There is no "I" in "T-E-A-M". A team falls apart when members begin participating in backstabbing, which often results in negative alliances being formed between members - while a sense of self preservation and distrust creeps around the otherwise neutral team members. Soon the team digresses into a group of individuals operating in silos. I don't think it's possible to put a finger on the catalyst for the entire process, but it could boil down to a combination of: an overly cynical team member, a preexisting alliance between team members, lack of leadership on the project, a team member with an unexplainable need for political control (perhaps lack of confidence in their abilities), a dysfunctional working environment, or human nature?...

No individual is a success who hurts the team, and no individual is a failure who helps it.- Software Project Survival Guide

How can we cope? Bottom line: RESPECT ALL YOUR TEAM MEMBERS. Treat your team as family, recognize that everyone has different strengths and weaknesses. Don't participate in backstabbing, be transparent and honest, if you have an issue with a team member then make it a point to discuss your concerns with that member. Anyone participating in backstabbing is hurting the team.

Nobody on the team should feel unappreciated or ignored. This ensures high level of motivation and encourages loyalty toward the team, and the goal of the project.  - Respect, Extreme Programming Values

A project's success hinges tightly on the team. Being a team player and having great interpersonal skills can be more important than technical skills - most people can rapidly learn new technical skills, but being able to function within a team might be an ingrained personality characteristic.