I found that not only BBC, but any realplayer video stream from any other website would also give "Playback error" on opening in VideoPlayer. I finally gave up and called Nokia support. They suggested flashing my 770 afresh with the latest firmware (though it was already up-to-date on my 770 which was bought about two months ago). Now videoplayer works again and I am able to see BBC News player video clips as well as others. I will have to re-install all the applications from maemo.org once again