Thanks very much for your help Jeramie, I am using the files you uploaded plus the thumbnail amendments and all is back to working as it was before. I wondered if you or one of the other posters could shed any light on a couple of small problems that I have had with the youtubeservice module throughout, which is that neither the pagination nor sort order ever seem to work.
If I limit the videos per page to less than the total number it just shows that number of videos, the same number as the total at the bottom of the page, and no pagination links or text.
Whatever I specify for the sort order, it never changes and I'm not sure what they are being sorted on by default.
I get the impression that this may be a YouTube thing rather than a problem with the SilverStripe module, but I'd be grateful for any further information.