For future reference (and to ease my searching in the future, as I forgot to write down the text when I got the error :), here are the dialogs you get if you try to run Realm Works when it it feels your computer has changed and it cannot talk to the server:
Realm Works No Connection 1.png
Unable to contact the server to properly register this machine. Realm Works cannot continue until the machine has been properly registered with the server.
Realm Works No Connection 2.png
Realm Works is exiting as it cannot continue without contacting the server.
Personally, it would be nice if you could continue read-only with an otherwise valid master.realm file, but I don't see them enabling that due to piracy. :(