On the PTR, I selected The Cataclysm in Chromie Time. However, I picked up and followed the questline started by Nazgrim in Orgrimmar that takes you to the zeppelin (hellscream’s fist?) to go to Pandaria. After turning in the quest on the zeppelin and going through the small loading screen that takes me to Pandaria, I immediately got disconnected with the error " A streaming error has occured. WOW51900322). After that, I can’t log back into that character without getting d/ced with the same error message.
If waiting 15-30 minutes logged out of that character doesn’t help, try putting in a ticket using the “Character Stuck” option.