I used to use a flv embed link into JW Player by http://corbilla.com/proxyyt2.php?id=<video_id_here>.flv where video_id_here is the video id in youtube, however no longer work, so either youtube has changed its code to not allow the direct flv links or there maybe some problesm in their server ...
It may be that particular video has been deleted... have you tried to check directly on youtube if the video is working on their site?
Yes I checked Here is the actual video http://www.youtube.com/watch?v=BfGSeD_fumQ and here is what used to work to extract the flv link from the youtube_vedie as below http://corbilla.com/proxyyt2.php?id=BfGSeD_fumQ.flv but seems, no longer works... ..