PDOException: "1052 Column 'uid' in where clause is ambiguous"

On node save i have error:
"PDOException: SQLSTATE[23000]: Integrity constraint violation: 1052 Column 'uid' in where clause is ambiguous:
SELECT u.uid AS uid, u.name AS name, u.status AS status, r.rid AS rid FROM {users} u
INNER JOIN {users_roles} r ON u.uid = r.uid WHERE (u.status IN (:db_condition_placeholder_0, :db_condition_placeholder_1)) AND (r.rid IN (:db_condition_placeholder_2, :db_condition_placeholder_3, :db_condition_placeholder_4, :db_condition_placeholder_5, :db_condition_placeholder_6)) AND (uid IN (:db_condition_placeholder_7)) ORDER BY name ASC;
Array (
[:db_condition_placeholder_0] => 1
[:db_condition_placeholder_1] => 0
[:db_condition_placeholder_2] => 5
[:db_condition_placeholder_3] => 0
[:db_condition_placeholder_4] => 0
[:db_condition_placeholder_5] => 0
[:db_condition_placeholder_6] => 0
[:db_condition_placeholder_7] => 7 ) in _user_reference_potential_references_standard() (line 491 of /....../sites/all/modules/references/user_reference/user_reference.module)."

Replacing next strings:

  $user_uid_alias    = $query->addField('u', 'uid');
  $user_name_alias   = $query->addField('u', 'name');
  $user_status_alias = $query->addField('u', 'status');

in user_reference.module to

  $user_uid_alias    = 'u.'.$query->addField('u', 'uid');
  $user_name_alias   = 'u.'.$query->addField('u', 'name');
  $user_status_alias = 'u.'.$query->addField('u', 'status');

solved the problem.