I'm sorry that I don't have a solution but you can try going directly to the TNT website www.tntdrama.com and watch from there; not a real solution but a workaround.
You can try and private message one of the Comcasty people and ask for assistance; but there's been no official repsonse from any of the Comcast people in any of the multiple threads where people are reporting this 422 error.
- Norm