Caching interfering with jQuery and drupal behaviors?
Just like when you add a menu item or some theme elements, you need to clear the cache when you add new javascript.

For a site in development mode you can simply turn off caching so that you don't have to remember to clear the cache every time ('drush cc all' is handy):

Drupal 6: /admin/settings/performance: Caching mode set to disabled

Drupal 7: /admin/config/development/performance: Uncheck cache pages for anonymous users

Disabling "aggregate javascript", will make it much easier to debug your js with chrome or firebug.