404 error after failed login

When users enter incorrect login information, they are given a 404 error page, rather than being asked to re-enter their credentials. I’ve tried turning off TML redirection, and the problem persists. Got any ideas?

Here are some screenshots, hosted on Imgr:
Before: http://imgur.com/1jQwJoA
After: http://imgur.com/Uc3Unzv

https://wordpress.org/plugins/theme-my-login/