Thank you for the reports. We did see a sudden spike in players receiving these error messages, but it should be resolved. For anyone who received a game/match loss because of it, please contact Customer Support.
Follow-up to this: If you do contact customer support, please include your output logs. We're still looking into what happened, so any additional information you can provide will be greatly appreciated.
Wizards Megan
Follow-up to this: If you do contact customer support, please include your output logs. We're still looking into what happened, so any additional information you can provide will be greatly appreciated.