You cannot change the system runmode from author->publish (or vice versa) after starting CQ for the first time.
Use a fresh CQ instance and start it in the runmode you need.
Thanks -- David
you can change the runmode after the startup, that is not a problem. Maybe it does not only have the outcome you would expect.
Starting with CQ 5.5 the initial setup of ACLs is done based on the runmode. Also the setup of the intial redirect when you hit /. So it is not recommended.