I just changed the Password of my database at my hosting-provider.
I have changed my “wp-config.php” file and entered the new password.
Jus try to change the Password of your database and you will see this error-message within the “Forums”-page of your website.
Did you also change the DB password in your bb-config.php file as well?
/** MySQL database password */
define( 'BBDB_PASSWORD', 'xxxx' );