Chapter 8. The Theme System, Page 181
The snippet used to override the breadcrumb seems to be incorrect. When following the guidelines, the order Drupal pulls this information is either incorrect in the book, or is coded incorrectly.
The theme registry needs to be cleared in order for new template overrides to be active.
To clear the theme registry, do one of the following things:
1. On the "Administer > Site configuration > Performance" page, click on the "Clear cached data" button.
2. With devel block enabled (comes with devel module), click the "Empty cache" link.
3. The API function drupal_rebuild_theme_registry.
More information can be found here: http://drupal.org/node/173880#theme-registry
