So I often noticed the error when you e.g. clicks on the messenger or logs out and wants to log in again directly.

I've observed this with Opera, IE and Firefox browsers - as soon as you log out and want to log in directly, you have a rotation between the login page and the registration page, but you can't log in, you have to wait about 15 minutes, then does it work again or via a different browser, then it works too.

At first I thought it was because of my server change, but it also appeared after the complete reinstallation and the last update on B1