Orbiter after closing simulation window should redisplay its launchpad if you haven't changed the shutdown option. Isn't it displaying it for you?
Is it a clean installation or add-on heavy?
Is it always this way or only when you use specific add-ons? What add-ons?
Did you try to terminate orbiter.exe process in task manager instead of restarting the system?
Did you try changing the Orbiter shutdown option in Extra tab, Debugging category to "Respawn Orbiter process" or "Terminate Orbiter process" to check if it helps your case?