You can log back in here.
It's like this all over the site.
Screenshot
Edited to add: Right after I posted this, it fixed itself.
That happens when the site is lagging and doesn't load right. You'll find this a lot during events, probably.
All right, I'm still a bit new so I'll remember that for later. Thanks. :)
Glad I'm not the only person this happened to. That was an annoying 5 minutes.