What are some issues that could keep the use of an enterprise resource planning system from being successful?

Consider a project manager with a team of 15 to 20 people: a mixture of analysts, designers, programmers and support staff. The project also uses some specialist staff on a part-time basis. How could the project manager influence the working environment of such a team so as to get the best out of them?

How can application software improve the effectiveness of a large enterprise? What are some of the benefits associated with implementation of an enterprise resource planning system? What are some issues that could keep the use of an enterprise resource planning system from being successful?