Lack of experience or skills. You'll have a tough time meeting your project milestones and deadlines without experienced senior leaders who possess the skills or knowledge needed in each project phase. For each core project area, you need a team member designated to provide answers in that area. Your team cannot set and maintain direction with a key position left unfilled for a long period, or with more than one such position left unfilled even briefly. Be wary when you find that reasonable challenges to the schedule, business model, or technology are discarded as the ranting of complainers, naysayers, or nonbelievers.
Good communication is imperative in interdependent teams.
To avoid problems, communicate frequently about project tasks and their prioritization on all teams' lists. Make sure someone on your team attends the other groups' meetings and vice versa. Status reports that blame others. Unquestionably, a team can be derailed by the failings of its dependencies, but if that's offered as a reason for increasingly bleak status reports, you've got a problem. Team members should be making alternative plans or falling back on contingency strategies instead of throwing up their collective hands and blaming their woes on others.