Clear the cache and the cookies from sites that cause problems.

• "Clear the Cache": Tools > Options > Advanced > Network > Offline Storage (Cache): "Clear Now"
• "Remove the Cookies" from sites causing problems: Tools > Options > Privacy > Cookies: "Show Cookies"

cleared cache and all cookies as you described. Still no luck, same problem.

You can try to change the protocol part of the link from http to a secure https

thx, but that didn't work either. Now ff keeps auto updating to 3.6.15 even though I have that turned off! (turned off via, tools, options, advanced, update). How do i prevent the auto update? update: upon closing firefox and reopening, I seem to get one video to play, but only one, then the remaining don't work.

I may have resolved this issue by installing the BetterPrivacy add-on and deleting all the lso cookies, then restarting firefox. Everything seems to be working now, will try to update in a couple of days. thx for the help.

When clearing the browser cache, set the period to Everything.

I had this problem recently and found my solution by starting FF in safe mode. Youtube videos played normally, so I guessed that one of my addons must be the culprit. I then found that disabling AdBlock (in normal mode and leaving all other addons functional) solved the problem. Also, AdBlock can be set to "disabled" for individual pages or websites, so that's what I did for YouTube.

I have the exact same problem. Any time I want to play a YouTube video I keep getting " En error has occurred. Try again later.". But my problem is not only with YouTube. Any time I want to play a video from withing Firefox, it does not play. Note that the problem happens only with Firefox. With IE I have no problems. I tried to clean cash and cookies. Did not help. I don't know what you mean by "safe mode". Can you give me more details as to how to do it. Thanks.