check this http://www.longtailvideo.com/support/jw-player/28836/media-format-support
the page says: "The JW Player tries to recognize a file format by its extension (e.g. .mp4 for MP4 videos). If the extension of your files is not recognized, the player will display an error. However, if you know your file is in a supported format, you can use the type playlist option to force the player to recognize the file as being of that format."
In your case the generated link for the video has no extension, so JW Player doesn't know how to play it.