What is wrong with this command?

   youtube-dl -o MontyPythonAndTheHolyGrail.flv "http://www.youtube.com/watch?v=eOfI88NKRzY"

It keeps telling me:

   [youtube] Setting language
   [youtube] eOfI88NKRzY: Downloading video webpage
   [youtube] eOfI88NKRzY: Downloading video info webpage
   [youtube] eOfI88NKRzY: Extracting video information

   ERROR: unable to download video

I've never had problems downloading videos before. I've tried getting rid of the '-o ...', getting rid of the quotes, getting rid of the space  after the '-o', but nothing works. What's wrong?
:-)~MIKE~(-: