You Tube altered their site and youtube-dl quit working. This has been fixed in the latest youtube-dl version. Version 4.7 will not have the fix but it is in current
http://openports.se/www/youtube-dl
If you go to the trouble of running current you will also find minitube as mentioned. It uses the qt4 libs and also needs the gstreamer-ffmpeg plugin
http://openports.se/multimedia/gstre...plugins-ffmpeg