On my 12.04 LTS I can't download from YouTube via youtube-dl. I used to do that, but recently (for a week) I'm not able. I tried on many videos and I get same output:
$ youtube-dl -t http://www.youtube.com/watch?v=Sh0ciyuXbJA
[youtube] Setting language
[youtube] Sh0ciyuXbJA: Downloading video webpage
[youtube] Sh0ciyuXbJA: Downloading video info webpage
[youtube] Sh0ciyuXbJA: Extracting video information
Traceback (most recent call last):
  File "/usr/bin/youtube-dl", line 4645, in <module>
    main()
  File "/usr/bin/youtube-dl", line 4636, in main
    _real_main()
  File "/usr/bin/youtube-dl", line 4620, in _real_main
    retcode = fd.download(all_urls)
  File "/usr/bin/youtube-dl", line 869, in download
    ie.extract(url)
  File "/usr/bin/youtube-dl", line 1135, in extract
    return self._real_extract(url)
  File "/usr/bin/youtube-dl", line 1406, in _real_extract
    url_map = dict((ud['itag'][0], ud['url'][0] + '&signature=' + ud['sig'][0]) for ud in url_data)
  File "/usr/bin/youtube-dl", line 1406, in <genexpr>
    url_map = dict((ud['itag'][0], ud['url'][0] + '&signature=' + ud['sig'][0]) for ud in url_data)
KeyError: 'sig'
It seems it's some signature problem. I still can download videos via vlc. But I like youtube-dl - its faster. I did already:
sudo apt-get --purge remove youtube-dl
sudo apt-get install youtube-dl
sudo youtube-dl --update
...but it didn't help.
 
     
    