MS SQL DB User Delete Failed

[arazas]

We are failed to delete DB user, the following error appears, We have MS Access based Plesk DB, please give us the solution.

Delete database user failed: Could not locate entry in sysdatabases for database 'kbo'. No entry found with that name. Make sure that the name is entered correctly.
---------------------- Debug Info -------------------------------
0: C:\Program Files\SWsoft\Plesk\admin\plib\DatabaseManagerMSSQL.php:52
DatabaseManagerMSSQL->dropUserImpl(string 'kbo', string 'kbo')
1: C:\Program Files\SWsoft\Plesk\admin\plib\DatabaseManager.php:136
DatabaseManager->deleteUser(object of type dbUser)
2: C:\Program Files\SWsoft\Plesk\admin\plib\class.DataBaseUsersList.php:126
DataBaseUsersList->remove(array)
3: C:\Program Files\SWsoft\Plesk\admin\htdocs\domains\databases\db_edit.php3:101