Girjet is a new charter airline and flies to several smaller airports to eastern europe beginning next summer. They currently sell almost all their flight for 0 Euros including tax. They might have a problem with their booking interface.

I successfully booked some flight for next summer, all for 0 Euros and already received an email confirmation.

Here is the link: http://kurflieger.air41.de/index.php?lang=english

Hope this might help someone!