Research on social capital has stressed the advantages that cohesive networks can bring to managers by helping them to secure cooperation from people in their organizations. Yet cohesive networks may also encumber the managers’ ability to adapt their networks to the shifting demands of their work. We explore this "dark side" of social capital using data from a newly created internal consulting unit within a large computer manufacturer. We show that managers with cohesive networks were less likely to adapt these networks to the change in coordination requirements prompted by their new assignments, which in turn jeopardized their role as facilitators of cooperation in within a newly created business unit structure. We conclude with a discussion on the trade-offs between different forms of social capital and their effects on effective management.