There is more than 2 GB of RAM free, also more than 20 GB available disk space on C:\

The sessionstore.js file should be updated regularly, as often as every 15 seconds if you are very active. Are you saying yours is not getting updated at all?

By the way, if you do not see the .js extension, you may need to turn on viewing of file extensions. See this Microsoft support article for the steps: http://support.microsoft.com/kb/865219.

For anyone visiting this thread who doesn't know the folder to check, you can access it from the Troubleshooting Information page. Either:

• Help > Troubleshooting Information
• type or paste about:support in the address bar and press Enter

In the first table, click the "Show Folder" button. For quickest reading, switch the view from icons to details, if it doesn't come up that way automatically.

I'm saying that my sessionstore.js was not updated at all for hours, for half a day... for a whole day... Then I tried to change the interval for updating the sessionstore.js file but nothing happened, nothing waked up maybe the broken service.

However it crashed before 30 mins with sessionstore file from this morning. CRAP... Is there are any file size restrictions for sessionstore.js which I can edit somewhere somehow?

Also I see that there is a file which is .bak file that contains some kind of back up for sessionstore.js, but it was at the same position as sessionstore.js, also It is maybe generated by some of the addons I installed trying to force browser to save session somehow, I don't know...

I tried to rename sessionstore.BAK to .js and the sessions was from this morning, nothing updated at all.

Can you say something more about the error log given by the session manager addon?

You can use this startup setting to make Firefox create a sessionstore.js file more often:

• Tools > Options > General > Startup: "When Firefox Starts": "Show my windows and tabs from last time"

• http://kb.mozillazine.org/Session_Restore

The error message sounds serious, but I've never seen it before.

When I search for some of the terms, I find various threads about a Firefox bug and what might trigger it. I don't see an obvious solution, but maybe these will give you some ideas:

• [Ext]Session Manager 0.8.0.8 - Aug 6, 2013 - mozillaZine Forums (links to bug that is still open)

• Issue 25 - tabgroupsmanager - Out of memory when saving session - TabGroups Manager Add-on for Firefox 19+ - Google Project Hosting.

Edit: fixed first link

You can check for problems with the sessionstore.js and sessionstore.bak files in the Firefox profile folder that store session data.

Delete the sessionstore.js file and possible sessionstore-##.js files with a number and sessionstore.bak in the Firefox profile folder.

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)
• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Multiple_profile_files_created

Deleting sessionstore.js will cause App Tabs and Tab Groups and open and closed (undo) tabs to get lost and you will have to recreate them (make a note or bookmark them if possible).

Also what I have noticed is that Firefox starts to use higher CPU and higher RAM capacity when working all day long without exit, but as I said I use hibernate functionality in the OS, so I won't look at the sessionstore.js and quit each time I found it's not updated...

Maybe the RAM limit in FF? is the key for my problem. It seems my problem is close to the one mentioned in this link http://forums.mozillazine.org/viewtopic.php?p=11668505

However, the problem is not solved.

If it works then yes helpfull

We have seen reports that Advanced SystemCare might possibly cause issues with session restore among other issues.
So if you have this software then you can consider to uninstall it.