You can check for problems with current Flash plugin versions and try these:

• disable a possible RealPlayer Browser Record Plugin extension for Firefox and update the RealPlayer if installed
• disable protected mode in Flash 11.3 and later
• disable hardware acceleration in the Flash plugin

• http://kb.mozillazine.org/Flash#Troubleshooting
• http://helpx.adobe.com/flash-player/kb/flash-player-113-crash-mozilla.html

If you have submitted crash reports then please post the IDs of one or more crash reports that have this format:

• bp-xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx

You can find the IDs of the submitted crash reports on the about:crashes page.

• You can open the about:crashes page via the location bar, like you open a website.

See:

• http://kb.mozillazine.org/Mozilla_Crash_Reporter
• https://support.mozilla.org/kb/Mozilla+Crash+Reporter

Ok so it seems that the enabling of Hardware acceleration was the issue here. That being the case, why is it that all of a sudden, it would being causing an issue with YouTube (as that is the only site causing the problem). I have never had to disable it before.

Also, will this reduce the performance of the web browser with sites using Flash?

I have this problem with Shockwave, too. I have Shockwave Flash v11.7.700.169. I keep getting a message that Shockwave stopped working and Mozilla crashes. Below are the crash reports:

b7fce51b-4fa3-4b8f-a15f-1334eb932125-flash2
b7fce51b-4fa3-4b8f-a15f-1334eb932125-flash1
b7fce51b-4fa3-4b8f-a15f-1334eb932125-browser
b7fce51b-4fa3-4b8f-a15f-1334eb932125

Can you help ?