OWA delay on frontend backend config

When I access OWA 2003 on our front-end server it is very slow to load messages once clicked or to do just about anything for that matter. It I access OWA directly off the backend server where my box is located than everthing is very fast no delay. Both the front and backend servers are exchange2003. The backend is a windows 2003 cluster. Why is it taking the front end soo long to proxy the request from the backend and serve it up to the client?