The event logs, both FMS and the OS for starters. Try to see what is going on. FMS should not quit like this so I would suspect that something is very wrong with the deployment.
What OS is this? What version of 15?
In the FMS admin console, if the statistics logging is not turned on (it's off by default - on the logging tab of 'database server') then turn it on; it will give valuable information on any bottlenecks that FMS is running into.