1. What did I do wrong?
2. How to fix?

I set up a new Debian instance and carefully followed the directions.

I got to the part where I was supposed to secure the system. I added a new user and confirmed the password--twice.

Now, I'm locked out as the new user and as root.

What to do?

Thanks in advance for any assistance you care to give...

Locked out how? Unable to access through SSH? Invalid user/password? Did you try it through Lish?

You can reset the root password from within the Linode Manager.

Yes. Locked out through SSH.
So, when I type: ssh username@111.11.11.111 (using actual credentials) it prompts for password and then says 'access denied.'

Have you created that user and password inside your Linode? By default Linodes are accessible via the username "root" and the password you set when deploying a distribution, they don't derive your username/password from your Linode Manager credentials.

If you have created that user, you'll likely want to log in via Lish to see why you can't connect: http://library.linode.com/troubleshooti ... node-shell

- Les

Many thanks, Les.
It ain't an adventure until there's all kinds of stuff that can go wrong...