Please uninstall Flash with this : https://helpx.adobe.com/flash-player/kb/uninstall-flash-player-windows.html

Flash Player Version: 27.0.0.187 Current Version https://get.adobe.com/flashplayer/otherversions/ Step 1: Select Operating System Step 2: Select A Version (Firefox, Win IE . . . .) Note: Other software is offered in the download. <Windows Only>

Copy/paste about:preferences into the Address Bar then Enter then down the page to Performance : Turn Off Hardware Acceleration.

Go to the Firefox 3 Bar Menu --> Help ? --> Troubleshooting Information Page and take a look in the Accessibility section if accessibility is set to "true" there. if yes, go to the Firefox 3 Bar Menu --> Options --> Privacy & Security panel and under Permissions check the setting to Prevent Accessibility Services from accessing your browser.

Restart Firefox

Please let us know if this solved your issue or if need further assistance.

Thank you for your quick reply.

Well, my question says that I already have the latest version of the flash player ruining, that is 27.0.0.187 Do you suggest to re-install it? That is to uninstall 27.0.0.187 and then install the same 27.0.0.187 again? Do you think that could be of any use?

My first post also says that I have already tried turning off this hardware acceleration and it does not help.

My accessibility is set to false. Do I need to change it to true? How?

I have ticked now this Prevent Accessibility Services from accessing my browser under Options --> Privacy & Security --> Permissions.

Appreciate your further clarifications! Many thanks!

klaipedaville said

Thank you for your quick reply. Well, my question says that I already have the latest version of the flash player ruining, that is 27.0.0.187 Do you suggest to re-install it? That is to uninstall 27.0.0.187 and then install the same 27.0.0.187 again? Do you think that could be of any use? My first post also says that I have already tried turning off this hardware acceleration and it does not help. My accessibility is set to false. Do I need to change it to true? How? I have ticked now this Prevent Accessibility Services from accessing my browser under Options --> Privacy & Security --> Permissions. Appreciate your further clarifications! Many thanks!

Correct : check the setting to Prevent Accessibility Services from accessing your browser.

No leave it as is, but remember .............as False

Ok so it does not help Hardware Acceleration Off........ I have not run into this as OFF and then been ticked.

Most always it is on and when ticked you would notice in Windows Task Manager up to 50% drop in use of ram. So that is how I would keep track, undo stuff that did, take tick out and see what happens.

What #'s are you getting now for ram usage ?

It does not hurt uninstall and reinstall as how many times has updates been copied over. You never know ,it is possible to cure issues this way.

Thank you for your follow ups.

Well, it still does not help reinstalling the same 27.0.0.187 version of the Adobe Flash player. Full screen mode crashes all the time.

I also tried all your other suggestions but it still crashes anyway...

I get 4.0/5.9 GB (68%) for RAM usage at the moment but I have a lot of other stuff running except for FF.

Any other ideas to stop Adobe Flash Player 27.0.0187 full screen crashing on Firefox Quantum? Thanks in advance!

https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode

Give above a shot it is sorta like what you have done but more stuff is turned off. See if problem persists. If does then get back , if does not then https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles Now will see as problem maybe in your profile. so backup then Make a new Profile https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles once made and restarted and are running from it then try full screen. Oh....Youtube does not use Flash, it uses HTML5 so ya best have video card drivers updated. See how it runs and get back.

Thanks. I was about to test it in safe mode myself.

I do not use any profiles. I just open a browser and start using it. Although I do have some plugins, themes, and extensions.

Youtube works fine in both small screen mode and full screen mode. My video and graphics drivers are up to date (as mentioned in my first post-question).

The Adobe Flash Player works OK in its small screen mode. It only crashes when I go full screen.

Will keep you posted.

Everyone has a Profile yours would just be smaller.

Doing Safe Mode disables all those while in Safe Mode so is better than turning them off.

So test in Safe Mode Test with a New Profile.

As for Flash as I say Youtube uses HTML5 so I do not know why Flash is crashing. Actually Youtube I think uses both, it just picks which one it will use.

Is it just Flash or does the whole browser crash ? If it is the whole browser then send the bp- files as instructed here : https://support.mozilla.org/en-US/kb/firefox-crashes-asking-support so they can be opened as a URL.

It's just flash that crashes when I go full screen, not the whole browser.

... but when I start it in a safe mode the Adobe Flash Player is disabled as well. I cannot run both at the same time, that is safe mode and Flash...

How about my favorite thing to do : uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files and C:\Program Files(x86) Then restart system. Then run Windows Disk Cleanup. Then run it again and click the button that says Cleanup System Files. Note: your Firefox Profile is saved. But you should make a back up before you do : https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

Reinstall with Current Release Firefox 57.0 with a Full Version Installer https://www.mozilla.org/firefox/all/

Along with a little Windows pick me up : Repair System Registry and Files

(FOR DOING Above & Below - WINDOWS All OTHER VERSIONS - Use Search To Find Command Prompt ** Enter CMD.exe to Find COMMAND PROMPT Then Right Click & RUN AS ADMIN)

To run the SFC command use the Windows key + X keyboard shortcut to open the Power User menu and select Command Prompt (Admin). Type "SFC /SCANNOW" (without quotes or copy/paste) and press Enter. For more information on using SFC, please refer to the Microsoft KB: Use the System File Checker tool to repair missing or corrupted system files

Run the Windows Deployment Image Servicing and Management (DISM) and System File Checker (SFC) tools as Administrator. The DISM and SFC tools scan the integrity of the Windows image and all protected system files replaces corrupted, damaged and incorrect versions. (FOR DOING Above & Below - WINDOWS All OTHER VERSIONS - Use Search To Find Command Prompt ** Enter CMD.exe to Find COMMAND PROMPT Then Right Click & RUN AS ADMIN) Type "DISM /Online /Cleanup-Image /RestoreHealth" (without quotes or copy/paste) and press Enter.

Windows 10 To run the DISM command use the Windows key + X keyboard shortcut to open the Power User menu, then select Command Prompt (Admin). Type "DISM /Online /Cleanup-Image /RestoreHealth" (without quotes or copy/paste) and press Enter. While running DISM you may notice the process will appear to pause at 20%. After a few minutes the operation will continue.

Note : SFC fixes files locally using files found on your system. Note : DISM goes up to Microsoft for new ones.

Wow.. Thank you. Appreciate your quick response and trying to help.... However, since a total and complete uninstall, some manual file deletion, and a thorough re-install seems to be the best option I think I will try to downgrade... Plus, I will definitely do this entire system clean up and integrity/corrupt files check first.... It's been a high time to do it really.. Not sure I need this update / new version if it makes me spend days changing stuff and figuring out how to deal with these new crazy "updates".