1) It means BT are too lazy to post an explaination anywhere or better still give the real meaning on-screen instead of a code.
2) BT phone help suggested my "LogIn" had expired. I was logged in.
3) BT online help was dysfunctional completely, that day.
4) a 9 times webmaster/programmer (me) has deduced it means the file is no longer available (time liimit).
5) Just say it, BT. Just say it.
And another thing........
Catch-up that is not yet available shows all the signs of being there, and you can click on the "Watch" logo, and it thinks about it, and offers the "watch" logo, ad nauseum. Why try 10 times? BT broadband quality, that's why.
Same problemo BT - you are a communication company that has difficulty communicating!