It sounds like your host has updated your mysql version.
Which means that your old encrypted password can't be converted to the new version.
First thing is to confirm what version of mysql you have now.
with a older version of ubb it may not be compatible with the mysql version.
Second if it is then you probably just need to re-enter a user name and password for the database.
If you can't keep the old username and password you will need to edit your config.inc.php file for ubb and make the changes.
