it is happening again, I thought I should mention it to the powers that be, in case it is indicative of an underlying problem, and not just BookCrossing gremlins.
I register a book using a pre-numbered label. No error messages. Seems to work fine. I *always* click on the book after registering to fix the book category as the site likes to change them to something else. But when I click on View Registered Book, I get a page to start registering a book. It doesn't indicate that this book is already registered or show any of the book information.
Just now, since it is happening again, I sorted my bookshelf by Recently Journaled. The book is there, showing up at the top of the list, cover picture and all, but when I click on it, I get the same screen with a blank space to enter a BCID to start the registration process.
Here's one of the books, though it has already fixed itself: http://www.bookcrossing.com/---/14762565
No response needed, it was just a brand new quirk to me yesterday so I thought someone should know since it is happening again.