For the past couple of months, one Exchange Server 2007 problem has plagued me. I had tried to install update rollup 3 in our organization. It worked fine on the front end servers, but certain services failed to start on the back ends. The Mail Submission, Mailbox Assistants, Replication Service, Search Indexer, and Service Host services all failed to "start in a timely manner." At that point, I punted and uninstalled the update.