They have now figured out why. They said "It looks like all of your databases are on the same mysql instance, with the exception of sfb2. So if we fix the permissions on one database then that will change the password and the next db will not work. Set up different usernames for each database. This will allow this to not happen again. So for the current db that is not working, add a new user and delete the current user, then update the wp-config.php file to have the new username and password you created.
Well why didn't they alert users during installation? Whereas in Site5 I wasn't given a choice on username and database names, that was actually good in hindsight, for people like me.
I guess I may have to give up on DreamHost.