how to troubleshoot flash player's protected mode for frefox?

1. Launch Real Player
2. click the Real  Player icon in the upper left corner of the window and choose Preferences
3. choose Download & Recording from the left hand panel
4. uncheck "Enable Web Download & Recording for these browsers"
5. Click OK and close Reakl Player
6. Restart FireFox

Não pude achar mais o site dessa resposta.
depois achei, aqui:  https://groups.google.com/a/googleproductforums.com/d/msg/youtube-pt/-/3dVVjOX430MJ
muito bom o Forum dos Produtos do Google > YouTube Fórum de Ajuda em
https://productforums.google.com/forum/#!msg/youtube-pt/teUbBHq8KE4/3dVVjOX430MJ