1. Re-install blockland.
2. Badspot maybe de-activated your account of online. (IDK how he works.)
3. Smash your computer, if your that mad.
I highly doubt this, I haven't done anything.
If your ID has been used or purchased by Piouyt or whatever his name is, it's been deactivated.
Has anything happened to your internet connection recently or have you changed any part of your home network setup?
wait, what did poiuyt do?
It's possible that your UDP and TCP are split over two connections. Your TCP IP is used for the authentication on the main menu while your UDP IP is used for authentication upon joining a server. Satellite/mobile broadband connections tend to do this.