Answers in this forum have shown different things have worked for different people.

For some clearing YouTube cookies and the cache solved the problem. For details of how to do that see https://support.mozilla.com/kb/Deleting+cookies and https://support.mozilla.com/kb/How+to+clear+the+cache

Others had to go a step further after deleting YouTube cookies and block YouTube from saving cookies. In the Tools menu select Options to open the Options window. Go to the Privacy panel and make sure it is set to "Use custom setting for history". Click the Exceptions button, type in http://www.youtube.com and click on Block

Another option is to disable hardware acceleration for Flash. To do that right-click on a Flash video, select Settings, go to the first tab of the settings for the option to enable/disable hardware acceleration for Flash. This is something recommended by YouTube for those having problems - http://www.google.com/support/youtube/bin/answer.py?&answer=1209379

You can also try changing to the secure YouTube site, https://www.youtube.com

I had deleted cookies and cleared the cache but that did not help. Apparently when I applied the setting to block Youtube from saving cookies that seemed to work.

Using the secure site (HTTPS) did not help.

Thank you very much for the tip.

This solved the issue. Thank you very much.

This is really strange. I believe this is a problem with Firefox code or Youtube changes; because, Youtube works with these solutions for most of us, but it works fine on other browsers. My wife's Windows 7 machine is locking up with standard streaming video on another site with Firefox (obviously a separate problem), but it works fine with another browser. On my Ubuntu machine, Chromium works fine where Firefox is not working unless I go to the secure Youtube site; however, other video sites appear to be working fine. This problem is very frustrating for users. What could be so different about the non-secure Youtube website. Apparently there is a key to solving this problem in there with the Firefox source code somewhere.

Can you please start a new thread for your problem or question.
Then you can also provide troubleshooting information like your operating system and installed extensions and installed plugins.

• [start a new thread]
• [/kb/Using+the+Troubleshooting+Informatio...]

Try to disable protected mode in the Flash player.

See:

• [/questions/929081]
• [/questions/928820#answer-340046]
• http://forums.adobe.com/thread/1018071?tstart=0

[locking thread due to the age]