Before going back to old version of firefox,can you go through these steps :

I guess crash happens due to flash ,since your version is outdated so update may help in this case. Get Adobe Also "Turn off Hardware acceleration" in Firefox :

• Menu>Options>Advanced>General>In the settings list, you should find the Use hardware acceleration when available checkbox. Uncheck this checkbox.

If all this not works then in reply put down crash report "Viewing crash reports" section fromSubmit Crash Report here.

At last You can choose the previous version of firefox from here :Firefox Directory .

Hi, you really shouldn't be having problems like that with the latest version, so please try Firefox Safe Mode to see if the problem goes away. Firefox Safe Mode is a troubleshooting mode that temporarily turns off hardware acceleration, resets some settings, and disables add-ons (extensions and themes).

If Firefox is open, you can restart in Firefox Safe Mode from the Help menu:

• Click the menu button , click Help and select Restart with Add-ons Disabled.

If Firefox is not running, you can start Firefox in Safe Mode as follows:

• On Windows: Hold the Shift key when you open the Firefox desktop or Start menu shortcut.
• On Mac: Hold the option key while starting Firefox.
• On Linux: Quit Firefox, go to your Terminal and run firefox -safe-mode
  (you may need to specify the Firefox installation path e.g. /usr/lib/firefox)

When the Firefox Safe Mode window appears, select "Start in Safe Mode".

If the issue is not present in Firefox Safe Mode, your problem is probably caused by an extension, theme, or hardware acceleration. Please follow the steps in the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article to find the cause.

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

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If Safe Mode didn't help, have a look at - Troubleshoot Firefox crashes (closing or quitting unexpectedly).

If you still want to use an older version - which isn't recommended because it may compromise your security, please see - Install an older version of Firefox.

This will show you how to change your update settings to manual - Install an older version of Firefox - (Update tab).

If your question is resolved by this or another answer, please take a minute to let us know. Thank you.