We're Sorry, This Video Is No Longer Available : YouTube

While watching Youtube videos sometimes an error comes saying that We're Sorry, This Video Is No Longer Available. Have a look :
This error comes when you have installed any download manager to your system. Now if you have installed any download manager, just open it and in the Options go to File Types. File Types includes the list of all the files that download manger handles. Just open it and remove .flv and .mp4 from the list.
Restart your machine and you are done. Now you can easily view all the Youtube vides without any error.