Working together, members on the Dutch forum tested, tried and poked around until they found a partial fix that members can apply themselves! Here's the recipe they came up with. It's a way to clear your list of the old, corrupted entries and start a new list that can be used.
1. Go to http://www.bookcrossing.com/managezones . You will need Wings to do this. If you need a free week of Wings to get your shortcut list going again, post a reply to this message and we'll hook you up.
The list at the bottom (your personal shortcut list) will look empty, despite the entries you remember it having. This is expected.
2. At the top of the page, click “select country”, then “state or province”, then pick a city and then an existing crossing zone. Add this zone to your list. It should appear there.
3. Now in a similar way, add all the Zones that you want on your list.
4. Don't forget to click the button at the bottom of the page to save your changes.
5. Go and release a book somewhere. The list should now be usable again. It will NOT contain your old entries, unfortunately; but from now on, the entries you just re-added will be usable again. We're not yet sure whether new Zones you use will be saved as they should; if you find out, let us know.
We hope this helps some of you. Thanks, Dutch BookCrossers and well done!