mysql error '1045: Access denied - Redmine Backup?

Sorry if this is just plain obvious but I'm being plagued with the mysql error '1045: Access denied for user xxx' when i try to do a mysqldump. None of my normal passwords work with 'root' as the user. Is there a manual way of backing up or is there a config file somewhere I can look at to get a hint of the password?

I installed phpmyadmin to try to work around the problem but it requires the same missing password.

Using mysqladmin -u root password xxxxx just gives me the same message (without the 1045 identifier)

Also is the database called redmine or railsapp_production by default?

Thanks

dld