Good Morning.
When changing passwords for Maximizer user accounts (including MASTER) then you must make the change in Maximizer. Open the Administrator and log into the address book in question, click File>>Users and highlight the user record you want to change the password for, then click 'Password' and change the account password.
When you click ok you will be asked if you want to make the change for just that address book or for all all address books, if you answer 'for all address books' the password will be updated for everything.
Be aware though that under MS SQL 2005 if your network uses a password policy then the SQL Server will also require the Maximizer Passwords to meet that criteria. An article explaining this, including a workaround can be found here:
support.maximizer.com/scripts/support.cfg/php.exe/enduser/std_adp.php?p_sid=RFNYpDti&p_lva=&p_refno=060403-000037