Case-based reasoning has been applied successfully to many diagnostic tasks, and much attention has been directed towards maximizing performance of the case-based diagnostic process. In distributed collaboration contexts, however, high-performance CBR alone may not be sufficient: individual abilities and organizational roles introduce unique constraints on how support should be applied. To maximize the usefulness of a case-based support system, system design must reflect divergent user capabilities and roles. This paper presents a case study of a CBR-based system to support collaborative distributed troubleshooting by ad hoc teams of sailors and shipboard experts. It shows how case sharing between participants can be used to increase confidence and aid situation assessment, "jump-starting" the aid process. It also shows how information from cases can be used to streamline communication between collaborators, and how the communication process needed to handle novel situations can be exploited as a natural vehicle for dialogue-driven generation of new cases to fill gaps in the existing case-base.