not sure right off the top of my head... can you check the application event log for errors and warnings during the Unity startup process? Might give us a clue what to look for. There should be a series of creates then inits then runs for each component in Unity, I'm hoping somewhere along the line something coughed up an error other than stating the service didn't respond in a timely manor.
also, is Exchange on or off the box? 55 or 2k?