Comment 3 for bug 608110

Also the solution detailed here (might also be listed on the links above): http://fedoraproject.org/wiki/Common_F13_bugs#Gnash_fails_to_play_youtube_videos

The GNU flash movie player (gnash) fails to play youtube videos (with necessary codecs installed) after the first youtube visit with the message : "An error occured, please try again later." inside the player. The problem appears to be due to mishandling of browser cookies. To workaround the issue, delete youtube cookies, then block cookies from youtube.

The procedure to remove cookies and block youtube.com cookies using firefox is listed below.

1. Open firefox preferences by selecting Edit → Preferences from the firefox menu
I2. n the preferences window, choose the Privacy tab
3. Under History, set the value of Firefox will to Use custom settings for history
4. Next, remove any youtube cookies by selecting Show Cookies. Enter youtube in the search box, and click "Remove Cookies". Close the Cookies dialog when finished.
5. Next, add an exception by selecting Exceptions and add http://www.youtube.com then select Block
6. Finally, close the firefox preferences dialog.