Problem: “Video Is No Longer Available” Error
It is possible that the video has been removed by the user who originally posted it. Solution: Please contact us so we can find another version of the video.
Problem: Video loading slowly or not playing
Possible Cause: Occasionally there are slowdowns of the YouTube (Dailymotion, etc.) servers. If the problem occurs all the time, it could be that your Internet connection is slow.
And here is another explanation and suggestion from YouTube Help
Check your actual download speed at: www.speedtest.net
For further Technical Support, please contact us.