Out of curiosity I have switched to Sickbeard and the same error is generated.
Is this a SAB problem?
Both apps show a connection when tested with SAB.
Yes I have. Most cases highlight a connection error between SAB and newsgroup.
I have tested mine and it is authenticated and connected to my subscribed newsgroup (and plenty of reserve quota).
It has happened before, and rectified itself, as I have not made any changes to SAB.
I'll leave it for a few days and see what happens.