No thumbnail on Youtube embedded in slider

Hi, I have a bit of an issue – a strange one, too, that seemed to pop up quite randomly, after working without a problem for a while now. I have a homepage slider on http://www.profoundcoaching.com.au/NEW/, with a Youtube clip that appears when clicked (autoplay is set to off.) Until this morning, however, this clip had a thumbnail as expected (the one generated by Youtube, which you can select after uploading the image; I did it myself, so I know that it was done correctly) — but then, after I edited something else entirely in the slide, the thumbnail has *disappeared*.

In its place is the ugly grey “default” thumbnail. When the image is clicked, the video plays normally, but that thumbnail is obviously quite ugly and uninviting – no one will bother to click on it and see the video, if there isn’t a visually pleasing image there to encourage them to.

Any help that anyone can offer would be *greatly* appreciated! Everything else on this site is ready to go, and we were *just* about to go live before this issue popped up.

Kind regards,

— Nathan