I'm not sure if this forum is an appropriate place to post this, but I assume someone from Ambrosia reads this from time to time:
I noticed that from time to time (esp. on Reefs island, or the first screen after coming back) it will display the "you cannot go any further without registering" message. If I save, quit, and then restart the game, the message goes away and everything is fine.
Anyways, that's the bug.
Greg