[darryl]

The main point is that you should only have the database itself connected to one instance of Calibre. If the connected instance is running the Content Server (I'm not sure aboutthe Wireless Connection), it is quite okay for multiple client's to connect to these. What you should not be doing is running more than one instance of Calibre itself accessing the database. So if you want to run Calibre itself on one of your desktops or notebooks to import books, edit metadata etc, you should shut down the instance on your headless server first to avoid possible problems. Always remember what you are doing is dangerous and you may run out of luck. So always keep good backups.