There are incorrect function names in the menu_breadcrumb.module on lines 323 and 332. The correct function name is
menu_set_active_menu_names instead of
menu_set_active_menu_name. The function name changed in D7 http://api.drupal.org/api/drupal/includes--menu.inc/function/menu_set_ac... .
I have attached a patch file. I wasn't sure if this should be appended to the discussion on issuecomment #18 or if this warranted a separate issue. Apologies in advance.