try going to the host name that you created in your broweser. does that load up for you?
If that is loading, then your database has been created, and the error is in the config of the phpbb. try and new install and make sure you select the cirrect host name and the caseSensitive user name/password.
If it's not loading for you something went wrong in creating the database. Check for it in your panel under goodies > mysql. If it's there, and dispalys the host name and user you have set up - it should logically be working. But seeing as it isn't I'd try deleting the database and starting all over again. Or you could put a ticket into support. Either way.
If it's not loading, and not listed in your panel, then the problem is that you didn't create the mysql database for the fourm to access. Create your datbase, create and user/pass , and create your hostname. Then try with your phpbb again.
If I'm crazy and way off the mark, then I'm sorry. but hopefully this will help.