The complexity of group interaction means that there are many uncertainties in the requirements for software support tools. Many existing software systems rely on the adaptability of human users to overcome such uncertainties. One of the biggest problems is that existing analysis techniques fail to predict how collaboration will change as a result of the introduction of a new system. In this paper, we demonstrate the extent to which group support systems can change an organisation. To address this problem, better theories of how collaboration evolves over time are required, and in particular, what aspects of collaboration are likely to lead to coordination breakdowns. This paper sketches out a model of collaboration based on concepts of shared understanding, conflict and breakdown, and analyses the mechanisms of interaction in the light of this model.