Occasionally I see the following error while visiting admin pages. Reloading the page I don't see the error anymore. The breadcrumb works fine. The only component that I have enabled is the base module "Custom breadcrumbs".

PDOException: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry 'fetch_task::custom_breadcrumbs' for key 'PRIMARY': INSERT INTO {cache_update} (cid, created) VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1); Array ( [:db_insert_placeholder_0] => fetch_task::custom_breadcrumbs [:db_insert_placeholder_1] => 1330194006 ) in _update_create_fetch_task() (line 245 of /var/www/drupal/modules/update/update.fetch.inc).

I have configured only one breadcrumb for a specific content type. Title and Paths setting read:

[node:content-type] [node:field-subject:0:name]
[node:field-subject:1:name]
[node:field-subject:2:name]

myview/my-type/[node:field-subject:0:tid]
myview/my-type/[node:field-subject:1:tid]
myview/my-type/[node:field-subject:2:tid]

where field subject is a term reference: hierarchical vocabulary with up to three levels terms (third term absent in specific case)