Try updating flash player: [http://get.adobe.com/es/flashplayer/ http://get.adobe.com/es/flashplayer/] Otherwise try youtube HTML5: [http://www.youtube.com/html5?gl=EN&hl=en http://www.youtube.com/html5?gl=EN&hl=en]

You can check for problems with current Shockwave Flash plugin versions and try this: *disable protected mode in the Flash plugin (Flash 11.3+ on Windows Vista and later) *disable hardware acceleration in the Flash plugin See also: *http://kb.mozillazine.org/Flash#Troubleshooting ---- It is possible that a reset carries over the problem to the new profile as it tries to import some data automatically. It is possible that the <i>cookies.sqlite</i> file that stores the cookies is corrupted if clearing cookies doesn't work. Rename (or delete) <b>cookies.sqlite</b> (cookies.sqlite.old) and delete other present cookies files like <b>cookies.sqlite-journal</b> in the Firefox profile folder in case the file cookies.sqlite got corrupted. *http://kb.mozillazine.org/Cookies *https://support.mozilla.org/kb/Deleting+cookies ---- Create a new profile as a test to check if your current profile is causing the problems. See "Creating a profile": *https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles *http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues If the new profile works then you can transfer some files from an existing profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over the problem *http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox