Ajax Error with DB contraint Issue

After having heartbeat running for a while, we got it crashed today with an ajax error and a Integrity constraint violation:

PDOException: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry 'heartbeat_activity-147-0-0-und' for key 1: INSERT INTO {field_data_field_my_message} (entity_type, entity_id, revision_id, bundle, delta, language, field_my_message_value, field_my_message_format) 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, :db_insert_placeholder_7); Array ( [:db_insert_placeholder_0] => heartbeat_activity [:db_insert_placeholder_1] => 147 [:db_insert_placeholder_2] => 147 [:db_insert_placeholder_3] => heartbeat_tweet [:db_insert_placeholder_4] => 0 [:db_insert_placeholder_5] => und [:db_insert_placeholder_6] => Hallo zusammen, bitte fleißig Nachrichten posten!! [:db_insert_placeholder_7] => ) in field_sql_storage_field_storage_write() (line 448 of /home/www/hosts/drupal/modules/field/modules/field_sql_storage/field_sql_storage.module).

After that posting the user saw his own message and another one which was not from him. But from that on no messages can be posted anymore, no messages will show up anymore.

Any idea to get the stream at least running again? Do we need to uninstall and install completely for that?