http://localhost:8080/ works, http://127.0.0.1:8080/ doesn't

What gives? When I view the page as "http://localhost:8080/" from the local machine, I can create the first (administrator) account and login without any problem. However, when I view the page from any other machine via it's public and/or private IPs, or even http://127.0.0.1:8080/ LOCALLY, I experience the "can't login or create the first (administrator) account" problem. What is going on?