WP security breaks login?

I first tried enabling WP security through wp-config a few years ago, and it didn’t work back then. I just updated to 3.8 and thought I’d try again, and it still doesn’t work. As soon as I enable it and attempt to log in, I am redirected right back to the login page again, no error. I’ve tried clearing cookies and using other computers, the same thing always happens. I don’t know what I’m doing wrong because it seems to be working for everyone else but me, so is there a catch? Everything I’ve read says you simply add the eight keys to wp-config with the random values from the WP key generator page and you’re set.

I’m on IIS 6.0, browsing with IE10.