I already asked this on Firefox support but still no anwer so maybe someone here knows how to fix this.
After I updated Firefox to version 39 I can't use it at all, it crashes all the time, I couldn't even write this question from Firefox. I clicked on "Refresh Firefox" button, also I restarted with addons disabled, also I reinstalled Firefox but none of that helps. Crashes are random, after 5-6 minutes of browsing.
You can see crash reports here: https://support.mozilla.org/en-US/questions/1071421
EDIT: I installed developer edition of Firefox and no crashes so far
After many attempts, I have a fix for this. The problem lies with Firefox version 39 and the Flash plugin. Either the Adobe or the Pepper flash.
What I have done is totally delete the flash plugins, install the Pepper flash, and download Firefox 39 from Mozilla, and overwrite Firefox 39, which came from the Ubuntu repositories.
The very first thing is to delete all Adobe flash installations
Now delete these with the purge option, using the file names returned from the dpkg-query command:
Now you can install the pepperflash from webupd8:
Now you will need to download the latest version of Firefox from Mozilla, as the version from Ubuntu seems to have issues. First step is to backup, for just in case something breaks:
Now you should be able to start Firefox and watch video without the constant crashes.
I have just updated from the trusty repositories with absolutely no problems.
With this type of problem, in the first place I would try to remove firefox completely and reinstall; something along the lines of:
(If you don't use/like aptitude, then apt-get should also work in much the same way.)
Another trick that sometimes has worked for me is to purge the caches Firefox uses. If you don't care about having to create anew your settings, bookmarks, etc., then you can clean all that up with:
and the next time you start up Firefox it should re-create appropriate directories automatically.
Failing this, it is also possible that an error exists in dependencies between packages, e.g. due to an incomplete installation of firefox without all the necessary dependent packages. In this case, upgrading completely the system can also be necessary:
The packages for Firefox version 38 still seem to be physically on the Ubuntu server (list here: http://archive.ubuntu.com/ubuntu/pool/universe/f/firefox/). Unfortunately, it does not seem possible to downgrade from 39 to 38 using the instructions found in the answers to previous question How to Downgrade a Package via apt-get? . apt-cache only knows about versions 39 and 28 at this time, has "forgotten" all intermediate versions.
Hope that helps.