If you are trying to register your database as a service on Mac OS X and after restarting your machine 4D does not launch, it may be because you do not have permission to write to the Mac StartupItems directory.
On Mac OS X when you register your database as a service files are written to the following directory:
This is a global directory, so you must have administrative rights to be able to write to it. Be sure to speak with your IT manager to ensure that your Mac OS X user account has such rights, or if you have access to the administrative account manage privileges as you see fit. Just make sure that the Mac OS X account you log into when registering your database as a service has the rights to write to the StartupItems directory.