Apart possible issues with Flash not being up-to-date, have you tried refreshing Firefox?

The Refresh feature (called "Reset" in older Firefox versions) can fix many issues by restoring Firefox to its factory default state while saving your bookmarks, history, passwords, cookies, and other essential information.

Note: When you use this feature, you will lose any extensions, toolbar customizations, and some preferences. See the Refresh Firefox - reset add-ons and settings article for more information.

To Refresh Firefox:

1. Open the Troubleshooting Information page using one of these methods:
   • Click the menu button , click help and select Troubleshooting Information. A new tab containing your troubleshooting information should open.
   • If you're unable to access the Help menu, type about:support in your address bar to bring up the Troubleshooting Information page.
2. At the top right corner of the page, you should see a button that says "Refresh Firefox" ("Reset Firefox" in older Firefox versions). Click on it.
3. Firefox will close. After the refresh process is completed, Firefox will show a window with the information that is imported.
4. Click Finish and Firefox will reopen.

Did this fix the problem? Please report back to us!

Thank you.

It did not help. I am enclosing 3 screenshots. 1 - it stalled. 2- YouTube message. 3- right click info for Flash. I would like to add that problems seemed to start after this Flash info started popping up. I had performed a DiscCheck, and the old Flash info popped up again. During that time, there was no locking up. Re-installing the current Flash, I got the current screen, and more locking up.

I'd suggest you to uninstall Flash from here and reinstall it, or to check the following instructions:

Some problems with Flash video playback can be resolved by disabling hardware acceleration in your Flash Player settings. (See this article for more information on using the Flash plugin in Firefox).

To disable hardware acceleration in Flash Player:

1. Go to this Adobe Flash Player Help page.
2. Right-click on the Flash Player logo on that page.
3. Click on Settings in the context menu. The Adobe Flash Player Settings screen will open.
4. Click on the icon at the bottom-left of the Adobe Flash Player Settings window to open the Display panel.
   
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5. Remove the check mark from Enable hardware acceleration.
6. Click Close to close the Adobe Flash Player Settings Window.
7. Restart Firefox.

This Flash Player Help - Display Settings page has more information on Flash Player hardware acceleration, if you're interested.

Does this solve the problem? Let us know.

Firefox relies on built-in OS support to play media files via the HTML5 media player. On the Windows XP platform you do not have native support for playing MP4 files with the HTML5 media player.

You can try if the solution posted here to add support for playing MP4 files works for you.

• http://www.msfn.org/board/topic/175591-enable-mp4-h264-aac-html5-video-in-firefox-on-windows-xp-without-flash/

Garrysch said

I am enclosing 3 screenshots. 1 - it stalled. 2- YouTube message. 3- right click info for Flash.

Thank you for the screenshots.

That's not the Flash player context menu, that's Google's custom right-click context menu for its HTML5 video player. Did the "Find out why" button on the blue bar below the player lead to any useful information?

Garrysch said

I use XP, SP3 for desk top. I bought a notebook with Win 10, and it hangs. When I right click to open in a new window, I often get "media not supported."

Where are you right-clicking? For example, a link to a different video? Windows 10 should have support for all of YouTube's formats through the Media Foundation, but you can check the tips in this article regarding filling in any gaps: Fix video and audio problems on Firefox for Windows N editions.

How can I by-pass HTML 5 and use only Flash? You have hit the problem on the nose. When the Adobe message box could pop up by right clicking, I never had this problem. Thank you members.

As far as I know, YouTube has ended support for Flash. I haven't seen any suggestions on this forum that there is a workaround to trick the site into serving Flash. You could search around on the web; it would have to be something in the past 60 days.

Next to your question under Question Details > More System Details you have the extension "YouTube™ Flash-HTML5" listed. I suggest removing that in case its efforts to modify how YouTube works are now causing more problems than it might have solved (although the non-anonymous reviews suggest it might not have been working well anyway).

Try this add-on: YouTube ALL HTML5 .

That extension won't help on Windows XP unless you would be able to add support to play MP4 files with the HTML5 media player.

Firefox relies on built-in OS support to play media files via the HTML5 media player. On the Windows XP platform you do not have native support for playing MP4 files with the HTML5 media player.

You can try if the solution posted here to add support for playing MP4 files works for you.

• http://www.msfn.org/board/topic/175591-enable-mp4-h264-aac-html5-video-in-firefox-on-windows-xp-without-flash/