I got an error message on creating a title field for a specific content type. After tthat the title was available by a views field but not in the content manger or on page view, on editing that node the title field was empty.
But I have deleted the title field and recreated it again. This time the batch gets until 97% and stuck there, no error message. But the titles are now available, all of them.

Hard to say how to reproduce this.

PDOException: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '' for key 'uri': INSERT INTO {file_managed} (filesize, status, timestamp, uuid) VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2, :db_insert_placeholder_3); Array ( [:db_insert_placeholder_0] => 0 [:db_insert_placeholder_1] => 1 [:db_insert_placeholder_2] => 1387294043 [:db_insert_placeholder_3] => bc4dd755-8c80-4b26-950c-c68efaf36f3a ) in drupal_write_record() (line 7170 of /srv/ht/root/pub/drupal/includes/common.inc).