Youtube Downloader is not working? Please ask the developer of the program about it.

As for online web-sites like download-youtube-videos.org, keepvid.com, savevid.com, keep-tube.com that were able to extract youtube links so that you can download Youtube videos, they don't really work anymore. Some of them ask you to copy the source of the page... well you can do that unless you're as lazy as me

There are many programs that still work. For example, Replay Media Catcher can download YouTube videos for FREE, freeware Freecorder 4 and Jaksta Free Media Recorder can save youtube videos, freeware firefox extension Fast Video Download can download youtube videos for free, ....

See the following thread for more:
YouTube video downloaders: How to Record/Capture/Download flash videos from YouTube