WD php: Warning: array_flip(): Can only flip STRING and INTEGER values! in DrupalDefaultEntityController->load()

Running the following command from drush:

drush upwd admin --password=secret

I get this output:

WD php: Warning: array_flip(): Can only flip STRING and INTEGER values! in DrupalDefaultEntityController->load() (line 167 of                     [warning]
/home/tkn//code/d7/includes/entity.inc).
WD php: Warning: array_flip(): Can only flip STRING and INTEGER values! in DrupalDefaultEntityController->cacheGet() (line 343 of                 [warning]
/home/tkn/code/d7/includes/entity.inc).
WD user: PDOException: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '' for key 'name': INSERT INTO {users} (uid, pass,   [error]
mail, created) VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2, :db_insert_placeholder_3); Array
(
    [:db_insert_placeholder_0] => 9
    [:db_insert_placeholder_1] => $S$C/eODyngYakMbrDAXkUPLn55TbQbO1r4eTjHmOFD5KDS7uepXrTO
    [:db_insert_placeholder_2] => 
    [:db_insert_placeholder_3] => 1286917853
)
 in drupal_write_record() (line 6468 of /home/tkn/code/d7/includes/common.inc).
WD php: PDOException: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '' for key 'name': INSERT INTO {users} (uid, pass,    [error]
mail, created) VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2, :db_insert_placeholder_3); Array
(
    [:db_insert_placeholder_0] => 9
    [:db_insert_placeholder_1] => $S$C/eODyngYakMbrDAXkUPLn55TbQbO1r4eTjHmOFD5KDS7uepXrTO
    [:db_insert_placeholder_2] => 
    [:db_insert_placeholder_3] => 1286917853
)
 in drupal_write_record() (line 6468 of /home/tkn/code/d7/includes/common.inc).
WD php: Warning: Cannot modify header information - headers already sent by (output started at /home/tkn/public/cvs-drush/includes/drush.inc:871) [warning]
in drupal_send_headers() (line 1048 of /home/tkn/code/d7/includes/bootstrap.inc).
PDOException: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '' for key 'name': INSERT INTO {users} (uid, pass, mail, created) VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2, :db_insert_placeholder_3); Array
(
    [:db_insert_placeholder_0] => 9
    [:db_insert_placeholder_1] => $S$C/eODyngYakMbrDAXkUPLn55TbQbO1r4eTjHmOFD5KDS7uepXrTO
    [:db_insert_placeholder_2] => 
    [:db_insert_placeholder_3] => 1286917853
)
 in drupal_write_record() (line 6468 of /home/tkn/code/d7/includes/common.inc).
Drush command could not be completed.                                                                                                             [error]

I'm running with HEAD version of drush. Don't know if that matters. Probably not.

This issue may be related to these two with similar error messages:

• http://drupal.org/node/937100
• http://drupal.org/node/547478