Hi Camedit, I am sorry to hear that this has happened on multiple updates. Does this happen from automatic updates, the About:Firefox page, or do you update with a stub installer?

Please also check to make sure that your settings are correct to restore the previous session.

Is "Restore from Previous Session" greyed out?

In the Location bar, type about:config and press Return.

# The about:config "This might void your warranty!" warning page may appear. Click I'll be careful, I promise! to continue to the about:config page. 

1. In the Search box at the top, type browser.sessionstore.resume_from_crash.
2. In the resulting grid, double-click on browser.sessionstore.resume_from_crash to set it to false.

I too have this problem and it's causing me a lot of stress. I have a number of tabs I like to keep pinned, plus I'm nearly always in the middle of using several unpinned tabs that I really don't wan to lose. Yet, when Firefox updates, of late, I am losing them.

I DO have my settings set to 'When Firefox starts: Show windows and tabs from last time'.

'Restore previous session' is greyed out.

Your about.config explanation uses the word 'crash'. This isn't a crash...it's just an update, so is that setting still relevant for losing tabs as a result of an update and not a crash?

Finally, I don't understand this whole Sync thing. There's not enough explanation in the browser settings to explain what it can be used for, or how it's supposed to work. As I understand it, it's supposed to save certain data to the cloud...does that include tab data? I am also only unsing one device at the moment, my laptop...so, if I sync my laptop data to the cloud, can I use that to restore open tab info when situations like this happen? All I see is 'Sync now' buttons, but nowhere to retrieve that synced info back onto my laptop, including tabs and personal colour settings that I dearly do not want to lose. Lastly, if I do click on 'Sync now' when I only had one tab open, do I lose all previously synced info, say, if I had a bunch of tabs synced, would I lose all those previously synced tabs and replace them with the one open tab?

It's quite incredible really...there's all this 'Sync' stuff in the menus, and in settings, yet there's no info on what it's purpose is. It's almost as if Mozilla expects us to instinctively know what it's for.

All I've ever wanted to do is save my colour preferences and my tabs, so that if I ever had to replace a computer, reinstall Firefox, or have this Firefox update thing happen to me, that I could just restore my tabs...yet, I've never been able to do this.