Can't upload more than 1 file using pgsql

Uploading the first file in a fresh installation with postgresql as database gives:

    * warning: pg_query() [function.pg-query]: Query failed: <br />
ERROR: relation "files_fid_seq" does not exist in  <br />/path_to_my_drupal_cvs_installation/includes/database.pgsql.inc on line 125.<br />
    * user warning: query: SELECT nextval('files_fid_seq') in <br />/path_to_my_drupal_cvs_installation/includes/database.pgsql.inc on line 144.

The file actually gets uploaded and a record with fid = 0 is written in the table {files}.
Subsequent uploads fail with those messages:

    * warning: pg_query() [function.pg-query]: Query failed: <br />ERROR: relation "files_fid_seq" does not exist in <br />/path_to_my_drupal_cvs_installation/includes/database.pgsql.inc on line 125.
    * user warning: query: SELECT nextval('files_fid_seq') in <br />/path_to_my_drupal_cvs_installation/includes/database.pgsql.inc on line 144.<br />
    * warning: pg_query() [function.pg-query]: Query failed: <br />ERROR: duplicate key violates unique constraint "files_pkey"<br /> in /path_to_my_drupal_cvs_installation/includes/database.pgsql.inc on line 125.
    * user warning: query: INSERT INTO files (fid, nid, filename, filepath, filemime, filesize)<br /> VALUES (0, 5347, 'edificio6.jpg', 'files/edificio6.jpg', 'image/jpeg', 42835) in <br />/path_to_my_drupal_cvs_installation/includes/database.pgsql.inc on line 144.<br />
    * warning: pg_query() [function.pg-query]: Query failed: <br />ERROR: duplicate key violates unique constraint "file_revisions_pkey"<br /> in /path_to_my_drupal_cvs_installation/includes/database.pgsql.inc on line 125.
    * user warning: query: <br />INSERT INTO file_revisions (fid, vid, list, description) <br />VALUES (0, 5347, 1, 'edificio6.jpg') <br />in /path_to_my_drupal_cvs_installation/includes/database.pgsql.inc on line 144.