As managers, we all want our employees to collaborate, work as a team, and play nice in the sandbox. When one employee comes to you with complaints about another employee, it can put you in a difficult position of having to arbitrate the dispute.
People have different viewpoints and, under the right set of circumstances, those differences escalate to conflict. How you handle that conflict determines whether it works to the team's advantage, or contributes to its demise.
Acknowledge the conflict! The conflict has to be acknowledged before it can be managed and resolved. The tendency is for people to ignore the first signs of conflict, perhaps as it seems trivial or difficult to differentiate from the healthy debate in a normal team. Once the team recognizes the issue, it can start the process of resolution.
Discuss the impact! As a team, identify and discuss the impacts the conflict is having on team dynamics, performance, and results.