Login Screen refreshing on submit (new install)

I work for a webhosting company who primarily builds sites in WordPress, and this is the second time I have noticed this problem. I set up a new site, go through the process of running the installation and database setup, then when I go to log in, the login page always just refreshes when you click the Log In button, regardless of the credentials entered. Because it’s a new site, caching and plugins should not be a concern.

The page I need help with: [log in to see the link]