Used BBC 1 catchup yesterday to see a prog from the start. Using the green button. Worked as usual.
On the same TV later that night, used catch up to watch the BBC1 news. About an hour after it had finished.
I-player wanted me to register this device - gave a code for this. Tried the BT Humax STB - same thing. Both had been working happily for ages. Did do this and it then worked OK.
Tried another TV in the house this morning. It didn't need registering again.