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 animation near the bottom of the page.
3. Click 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.

If my above post does not fix the issue, please try removing Adobe Flash Player from your computer completely.
Then reinstall it.

Hi ComputerWhiz,

Thanks a lot for your kind answer and for the accurate and very clear description of the proposed procedure. I already knew the two articles by Mozilla and Adobe: https://support.mozilla.org/en-US/kb/keep-flash-up-to-date-and-troubleshoot-problems http://www.macromedia.com/support/documentation/en/flashplayer/help/help01.html as well as the Adobe Flash Player Help page: http://helpx.adobe.com/flash-player.html

I already tried to follow this Help page before (and have tried it again after your message), but as you say in line 2 of your instructions (Right-click on the Flash Player animation near the bottom of the page), this is a Flash animation, and as a result, Firefox freezes IMMEDIATELY as soon as the Shockwave Flash module tries to interpret it. So I have NO chance to get a context menu with a right click (or a Ctrl click) that would allow me to disable the hardware acceleration in the Display control panel. Firefox freezes BEFORE I could right click!

Is there another way to disable this hardware acceleration in Firefox? As a comparison, I have checked the behavior of Safari: It works quite well with Flash content, without freezing, and I am able to right click on Flash animations to disable or enable hardware acceleration. But this seems to be a parameter local for Safari and not affecting Firefox. It would be nice to have a Web page with a Flash animation that does not starts playing automatically, so that I could right click on it before Firefox freezes. But all pages I have tried (with Safari) do start immediately playing the animations…

So the problem is NOT solved, and any new proposition will be welcome. I will answer your second message separately.

Hi again ComputerWhiz,

and thanks also for this second suggestion. I already tried to uninstall Adobe Flash Player, following the procedure described in: http://helpx.adobe.com/flash-player/kb/uninstall-flash-player-mac-os.html and to reinstall it in a subsequent step, but it did not changed anything: Firefox keeps freezing as soon as a Flash animation is present.

As I could not provide any detailed technical information on the system where I experience this problem when I posted my question (I posted it from another computer), I provide them now by editing the question and updating the troubleshooting system information. Please refer to it if you think it could be useful.

Do you have any other hint?

Try Firefox Safe Mode to see if the problem goes away. Safe Mode is a troubleshooting mode, which disables most add-ons.

(If you're not using it, switch to the Default theme.)

• On Windows you can open Firefox 4.0+ in Safe Mode by holding the Shift key when you open the Firefox desktop or Start menu shortcut.
• On Mac you can open Firefox 4.0+ in Safe Mode by holding the option key while starting Firefox.
• On Linux you can open Firefox 4.0+ in Safe Mode by quitting Firefox and then going to your Terminal and running: firefox -safe-mode (you may need to specify the Firefox installation path e.g. /usr/lib/firefox)
• Or open the Help menu and click on the Restart with Add-ons Disabled... menu item while Firefox is running.

Once you get the pop-up, just select "'Start in Safe Mode"

If the issue is not present in Firefox Safe Mode, your problem is probably caused by an extension, and you need to figure out which one. Please follow the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article for that.

To exit the Firefox Safe Mode, just close Firefox and wait a few seconds before opening Firefox for normal use again.

Please report back soon.

Hi ComputerWhiz,

Thanks again for your continued help. I am using only the Default theme. Following your instructions, I have started Firefox in Safemode, either with the option (alt) key pressed during Firefox starting up or by using the menu request "Restart with Add-ons Disabled", but the issue is still present in Safe Mode : Firefox freezes on the Adobe Flash Player Help page: http://helpx.adobe.com/flash-player.html

For your information, I enclose 3 screen captures showing the Extensions (add-ons), the Theme, and the Plugins when Firefox is in Normal mode. The only Extension (add-on) is "Troubleshooter 1.1a" installed recently to provide troubleshooting system information for this help request.

I have also checked the plugin status : Shockwave Flash 11.9 r900 (downloaded on Nov. 2nd) is now said to require an update. I have done it from http://get.adobe.com/fr/flashplayer/completion/?installer=Flash_Player_11_for_Mac_OS_X_10.6_-_10.9 So the version 11,9,900,117 has been replaced by the version 11,9,900,152 (versions checked by Safari on page http://www.adobe.com/fr/software/flash/about/). But Firefox keeps freezing when there is some Flash content (checked with http://helpx.adobe.com/flash-player.html and with http://www.adobe.com/fr/software/flash/about/).

In addition I have made the following test : deactivated the 8 first plugins (all except Shockwave Flash) and restarted Firefox, and then went to the pages : http://helpx.adobe.com/flash-player.html or http://www.adobe.com/fr/software/flash/about/. In both cases, Firefox still freezes and has to be killed.

What could I do next?

Does the flash content continue to play if there is a movement of the mouse.
Some Flash issues were discovered in Firefox 25.0, so we are asking all users to update to Firefox 25.0.1.

Please do so and report back soon.

Hi ComputerWhiz,

I am not sure to understand correctly your sentence "Does the flash content continue to play if there is a movement of the mouse" since, as Firefox is freezing immediately, the flash content never starts playing.

Anyhow, while Firefox was frozen, I have moved the mouse over the window and it did not make Firefox to revive.

Concerning the Firefox version, since the preferences were set on "automatically updating", it moved by itself to the 25.0.1 version, and I can confirm that the problem is still there with Firefox 25.0.1 and Shockwave Flash 11.9.900.152.

Coming back to one of my former ideas, it would be nice to have a Web page with Flash content that is not set to start automatically (seems that all ads start automatically). May be I would then have a chance to right click on the Flash frame! Unfortunately I have not been able to find such a page, if you know one of them, please let me know.

The Firefox add-on, Flashblock should stop Flash content from beginning automatically.

Hi ComputerWhiz,

Thanks for your quick reply. I have installed Flashblock 1.5.17 and restarted Firefox 25.0.1, but it still freezes on Flash content. Apparently Flash action is faster than Flashblock!

Since Flashblock says it does not work with Javascript disabled, I have reactivated Java Applet Module 13.9.8 in Firefox. Since the previous tests, all Plugins except Shockwave Flash had remind disabled, but anyway I am not sure that Java Applet is the same as Javascript, I am a bit lost in Java affairs… No change: Firefox keeps freezing on the Adobe Flash Player Help page: http://helpx.adobe.com/flash-player.html

Another way to prevent Flash animation from playing would be to put the Flash Plugin in the "Activate on demand" state.

In this case, and without Flashblock installed, Firefox does not freeze and the animation is replaced by a Lego like icon. But if I right click on it, I do not get the context menu that would allow me to disable the hardware acceleration in the Display control panel.

With Flash Plugin in the "Activate on demand" state, and with Flashblock installed, Firefox does not freeze either and the animation is replaced by a Flashblock icon. If I let the mouse fly over this icon, it turns to a "Start arrow", and if I left click on it, it turns to the Flash Lego like icon, and I am back to the previous case. If I right click on the "Start arrow", I get a pop-up menu with various options related to Flashblock, but not the Display control panel.

Hi ComputerWhiz,

10 days have gone since our last exchange, and my problem is still there! Do you have any additional hint to try?

My Mac is running with Firefox 25.0.1 and Flash 11.9.900.152 which are up to date as far as I know. Are there any new version in preparation that could cure this tricky problem?

Cheers,

This sounds like the sort of problem that requires you to completely uninstall Flash Player and Firefox (use AppCleaner), reboot the Mac, and then re-install Firefox from scratch. Reboot again, and install Flash Player from scratch.

I doubt that the software is incompatible with the OS; if it was, given all the people still running Snow Leopard, we'd have heard a lot more howling about it by now. (I assume you need 10.6.8 to run a Power PC application under Rosetta.) If the problem persists, the most likely explanation is that your OS got dented somewhere along the line. Hope you've got the Snow Leopard install discs on hand...

Hi, jpdemers , and thanks for your advices.

I have been travelling for some time and was not in position to make any new test for about two weeks (the affected machine is an iMac at home). Today I have uninstalled Firefox using AppCleaner, as well as Flash Player using Adobe uninstall_flash_player_osx.dmg ; and I have then installed both of them from scratch. Unfortunately the problem is still there :-(

I just notice that I forgot to reboot the iMac (twice) as you said. I believe it may not be so important, but I will repeat the cycle with the reboots included (early next year now !). I will keep you updated on the issue, and I hope I will not have to reinstall the system. I have the install discs, but this may be an heavy burden...

In the meanwhile, I wish you an happy new year !

Good luck . . . I agree that the re-boots aren't likely to be the magic solution. I do it just to be on the safe side, so each installer knows exactly what's running.

Have you checked out the Flash Player control panel in System Preferences? There's an advanced setting that lets you erase all saved settings and files, and that's probably worth a try.

Since your installation of Safari handles Flash without a problem, I'm more optimistic about solutions that tweak Firefox. Harware acceleration can be turned off in Firefox: Preferences/Advanced/General; uncheck hardware acceleration under "Browsing".

You might want to back down to an earlier version of the Flash plugin, and see if the problem goes away: http://helpx.adobe.com/flash-player/kb/archived-flash-player-versions.html#main_Archived_versions

Failing that, you might want to back down to an earlier version of Firefox.

For whichever one(s) work, keep the installer handy, so you can test future versions and easily revert if necessary.

Isn't it just typical that the user gets blamed for using the wrong add-ons, or not disabling certain things. Every time I re-load Firefox, it works fine, until I download Flash Player, then bang.

Simple answer to this. Much as I hate to say this, but I have started using Chrome, without the problems with Firefox. Youtube and other progs work fine in Chrome.

At this rate, Mozilla will loose all its customers. This kind of response is not good enough.

Hi, I solved this shit.

Flash video/content crashes instantly, so it makes it impossible to right-click it and enter the settings to disable hardware acceleration. This issue wasn't solved for over 2 years in other forum posts, but I finally did it. You have to temporarily DISABLE all your recording and playback devices in the windows' sound menu. this will let you play flash content (it did help me), just enough to disable hardware accelertion. I am suprized Mozilla survived despite being unable to debug their own software - no respect to customers ad their time.