Cannot login: What did I do wrong

About a month ago, I went through the various settings for this great plugin and locked down my site. Now, when I try to login, I cannot. When I try to access <site>/wp-admin, I get ‘Not available’; and when I try to access <site>/wp-login.php, I get ‘This page cannot be found’.

The work around is to move the All-in-One folder, login, then move it back.

Clearly, I set some control incorrectly. I checked the User Login section, but that seems to be okay. Can you please help me figure out what I did wrong?

Thanks!