Okay, so there apparently was an issue with the Twitch nickname reclaim tokens. It -should- be fixed now, but if you come across an issue when logging in with your Twitch account, please reply to this thread (try logging out and back in again, first). Once you have successfully logged in, you should be able to reclaim your old account name.
somebody pin this, or put it on front page. thanks a lot for this.
No more BlackcurseLT, long live user-8399056