Protected Content page doesn't log in

Hi, I'm using Membership 2 Pro to protect content.

When a user logs in and browses to content that is under their membership, everything is fine.

But if they go to protected content when not logged in, they see the Protected Content page with the login box. Even if they put in the correct credentials, the form does not log in and they get stuck on that page. Check out the screenshot - you can see where it says it is Logging In... but then bounces back to that page.