Hmm, those two crash reports are from June 15th. Did you give up on Firefox in the intervening weeks?

Have you made backups of your current sessionstore files in a safe location for future reference? The files would be in your currently active profile folder. To open that from outside Firefox, you can paste the following in the search box on the start menu and press Enter:

%APPDATA%\Mozilla\Firefox\Profiles

You may see one, or more than one, partially-randomly-named folders here. Click into the folder(s) and look for the most recent sessionstore.js, sessionstore.bak, and other sessionstore files. Copy them to a safe location such as your Documents folder.

Note: If Windows does not display the file extension, turn them on using the method in this article: http://support.microsoft.com/kb/865219.

Do you have Firefox set to only load the last active tab in each window (default setting), or is it trying to load all tabs in all windows? If you have customized this, you could try going back to the default setting. This is a simple checkbox in the Options dialog, but if you can't access the Options dialog because Firefox doesn't let you use the menus, you could change the setting "the hard way" by manually editing a JavaScript file (prefs.js) to remove the custom setting.

More info if needed.

If you do have to give up on restoring your last session, there are a few methods for extracting the URLs from the sessionstore.js/.bak files you copied to a safe location so that even if you can't restore the exact tab state (with cookies and easy back-forward history) you can at least load those tabs from their URLs. These threads have suggestions on how to "mine" the old file to extract the URLs:

• Using Firefox's Browser Console (formerly known as Error Console): https://support.mozilla.org/en-US/questions/969046#answer-471950
  Using Firefox developer tool "Scratchpad": http://dev.jeffersonscher.com/sessionstore_reader.html (this is a more stylized version of the next option)

• Using Firefox developer tool "Scratchpad": http://forums.mozillazine.org/viewtopic.php?f=38&t=622036&start=60&p=12098147#p12098147

• Using a third party website: https://firefox-session-restore.herokuapp.com/

Your memory usage is very high on both reports

Crash Report ID: 6623d1e0-8584-4b63-b93b-3f54d2140615 2014-06-15 17:02:54.864555 https://crash-stats.mozilla.com/report/index/6623d1e0-8584-4b63-b93b-3f54d2140615

Total Virtual Memory 2147352576

Available Virtual Memory 223924224

System Memory Use Percentage 70

Available Page File 4661026816

Available Physical Memory 1089470464

Look up bug reports here.

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Thanks for the replies. I had already backed up my sessions, and Firefox is set to only load the last active tab. Yes, I mostly gave up on Firefox for a few weeks out of frustration, but also a lot of the time it would crash and shut down before I had the chance to send an error report. Those two were the only ones that managed to get through in time since this issue started.

My memory use is very high, probably because of the amount of tabs I had open due to a research project. I've been trying to reduce the tabs, but have had the same amount open for months with no previous crash issues, so I don't think that's the cause of the problem.

Since my first post I uninstalled Firefox completely and reinstalled it (rather than just re-installing over the original installation as I'd done previously). It hasn't crashed yet but now it's taking about 5 minutes to load the last tab, and only slightly less time if I try and load any other tab so it's still pretty much unusable.

Spoke too soon, it's started crashing again :(

Uninstalling and reinstalling Firefox -- assuming you do not remove your personal data, which means your bookmarks, history, settings, etc. -- only helps when the program files are damaged.

To test how Firefox runs "uncustomized" on your system, could you do a three-minute experiment?

Create a new Firefox profile

A new profile will have your system-installed plugins (e.g., Flash) and extensions (e.g., security suite toolbars), but no themes, other extensions, or other customizations. It also should have completely fresh settings databases and a fresh cache folder. This test is answer the question "what if" you reset to factory defaults — without actually affecting your current settings.

Exit Firefox and start up in the Profile Manager using Start > search box (or Run):

firefox.exe -P

Do not delete anything here.

Any time you want to switch profiles, exit Firefox and return to this dialog.

Click the Create Profile button, assign a name like Test, and skip the option to change the folder location. Then start Firefox in the new profile you created.

Does it start up any better? If you change the setting to your preferred start page, exit, and start Firefox again, is it any different? If it's snappy, that provides reason for hope that we can root out the problem in your regular profile and have Firefox working normally again.

When returning to the Profile Manager, you might be tempted to use the Delete Profile button on Test. But... it's a bit too easy to accidentally delete your "real" profile, so I recommend resisting the temptation. If you do want to clean up later, I suggest making a backup of all your profiles first in case something were to go wrong.

OK, I've tried what you said and have no problems when using the new profile. I've also experimented with the old profile by starting a new session and that works ok too. Loading any of my historical sessions (whether they had 2 tabs or 200) causes Firefox to crash, so the problem is narrowed down to any Session Manager files created before the Firefox upgrade.

I could extract the tab URLs and start all over again but I have so many of them that it would take ages. Is there a way to find and fix the problem with the last session?

I'm not aware of a general purpose tool to "clean" a sessionstore file so it can be used as a sessionstore file. The closest I know of are the techniques mentioned earlier to scrounge the URLs out of the file.

The procedure I mentioned before for running in the Browser Console no longer works. I'm going to have to document a different way to run it. For now, you could try the second and/or third of those options.

https://support.mozilla.org/questions/1009984#answer-601548

7/20/2014 : Updated my variation of the script to run in the Scratchpad, with updated directions related to using that tool: http://dev.jeffersonscher.com/sessionstore_reader.html

https://firefox-session-restore.herokuapp.com/ Firefox Session Restore