I am getting the following error when saving a field that is attached to a comment. Increasing the cck_field_settings.bundle column from varchar(32) to varchar(128) fixed the issue. 128 is the size of all the core field_* tables' bundle columns.

PDOException: SQLSTATE[22001]: String data, right truncated: 1406 Data too long for column 'bundle' at row 1: INSERT INTO {cck_field_settings} (field_name, entity_type, bundle, language, setting_type, setting, setting_option) VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2, :db_insert_placeholder_3, :db_insert_placeholder_4, :db_insert_placeholder_5, :db_insert_placeholder_6); Array ( [:db_insert_placeholder_0] => field_report_ran [:db_insert_placeholder_1] => comment [:db_insert_placeholder_2] => comment_node_report_registry_report [:db_insert_placeholder_3] => und [:db_insert_placeholder_4] => instance [:db_insert_placeholder_5] => default_value_php [:db_insert_placeholder_6] => ) in drupal_write_record() (line 7036 of /xxxxx/includes/common.inc).