Drupal version is 7.22.
It may be worth mentionning that it was previously upgaded from a former drupal 6.x website, following recommandations for the update.

The error seems to be the following:

PDOException: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry 'Full HTML' for key 'name': INSERT INTO {filter_format} (format, name, cache, status, weight) VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2, :db_insert_placeholder_3, :db_insert_placeholder_4); Array ( [:db_insert_placeholder_0] => full_html [:db_insert_placeholder_1] => Full HTML [:db_insert_placeholder_2] => 1 [:db_insert_placeholder_3] => 1 [:db_insert_placeholder_4] => -10 ) in filter_format_save() (line 217 of C:\wamp\www\integ-europe.com\modules\filter\filter.module).