There was another user that had this issue and saw that if they restarted in Safe Mode that all of the windows would be restored. Can you confirm if this is the same?

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.

When you figure out what's causing your issues, please let us know. It might help others with the same problem.

Hi, Thanks for the reply and help ! Im not sure whether it will work yet

I'm still waiting for the problem to re-happen again. I will try out the method you suggested once it does.

Anyway my list of Addons are as followers : - Adblock Plus - Adblock Plus Pop-up Addon - BitComet Video Downloader - DownThemAll - Easy Youtube Video Downloader Express - Karma Blocker - Undo Closed Tabs Button

- OpenH264 Video Codec by Cisco system - Primetime content Decryption by Adobe Systems - Shockwave Flash - Nvidia 3D Vision - Nvidia 3D Vision (Streaming plugin)

Also I realised it usually happens when I have 4 windows of Tabs or more. Recently I leave only 3 Windows groups of Tabs on and it seems to be stable and stick to re-opening 3 windows.

I'm goner purposely open up to 4 groups of windows and and see if the problem is more frequent.

Thanks again buddy

Make sure to close Firefox using the "Exit" command, either:

• "3-bar" menu button > "power" button
• (menu bar) File > Exit

The reason being, if you let Windows shut down Firefox, it does so by sending consecutive close window commands and, by default, Firefox only remembers three closed windows. The Exit command does not mark any of the windows as closed when shutting down Firefox so they should all restore automatically regardless of number.

Also, for safety in case you don't always use Exit, you can increase the number of closed windows that Firefox remembers by changing a setting here:

(1) In a new tab, type or paste about:config in the address bar and press Enter. Click the button promising to be careful.

(2) In the search box above the list, type or paste sess and pause while the list is filtered

(3) Double-click the browser.sessionstore.max_windows_undo preference and increase the value from 3 to 10 (or value of your choice) and OK the change

Please be cautious in modifying the value of other session-related preferences to avoid disabling the feature. If in doubt, ask.

To jscher2000, Thank you so much for the suggestions ! And I believe is working now !! I tested it twice and it's working. I will continue to keep my windows above 3 for a while and post a feedback here again after some time.

Oh by the way I'm wondering has the default setting for this firefox setting been changed since the older versions ? Because I remember I have this problem only quite rarely a while ago while i was using windows7 and a slightly older firefox version.

To guigs2, I believe your method works too ! Didn't know safe mode can comes into use. I better remember it .. !

D You're guys are genius(s) man ..

Thanks everyone for the time and effort to help out.

Hmmm today the problem happened again. Too strange.. this time only 1 window remains.

Few days ago I've set the browser.sessionstore.max_windows_undo preference to "5".

I also tried the Safe mode method. Not working this time.

• _*

Did anything different happen between sessions, such as Firefox crashing, restarting Windows, etc.? If it's just random, hmm, hard to make any further suggestions.

Nothing unusual happened i think.. After i'm done with surfing, usually i just quit firefox, off my com. Next day, start com, start firefox.

Last night i tested again, I changed the browser.sessionstore.max_windows_undo preference to "4" before i off my com. Maybe for some reasons i thought maybe 5 is too much ? lol.

This morning when i opened firefox, it happened again, Left only 1 window with it's Tabs. Twice in a row now. strange ..

Ok there is one thing i should mention here. Is that i have a habit of going to Task Manager to close firefox rather than using the firefox menu quit option. Everytime when i restarted firefox it will just have the option for me to restore the previously 'crashed' session. The reason I use this method is that last time firefox always have this weird inconsistency problem with retaining my tabs, so i resorted to that method. Is a method that i'm used to for years and it works 99% of the time (even with the latest version) ... up until recently anyway. Do you think I should have use the 'quit' option from the menu instead?

OK. I just double tested it again.

Here's the weird thing. Here goes :

Latest no. of windows i left open is 2.

1) I used the Task manager to quit, relaunch, only 1 window came back.

2) Next, I re-created a new 2nd window, and quit using Menu>File>Exit. When relaunched, both windows came back. Good So I thought this is how it works huh.

3) Next, I re-test AGAIN by closing these 2 windows by using Task Manager again. Guess what ? 4 windows came back. 2 of the windows contains Tabs that looks like it's from a few previous sessions before.

This weird thing happened before .. long time ago. That for a while some windows I thought are gone forever. Then one day, randomly when i relaunched firefox on some fine day, a few extra window came back up again. Like they went on vacation and are back now. But it's super super super rare. like it ever happened to me 2-3 times in many years.

Now i wonder which is the more consistent method to relaunch Tabs/Windows :( :( This is exactly the reason why I opt to use the 'Task Manager' to exit ... in the first place. Anyway now it's not working too good either ..

Wow, well, one significant difference between using the Task Manager and using Exit is that when you use Exit, Firefox goes through an orderly process of updating files. In particular, it should finish updating the recovery.js "real time" session history file and move it to the profile folder and rename it sessionstore.js for the next startup.

Killing a program through Task Manager omits these cleanup steps and the results may be unpredictable. Or should I say, I can see from your test that the results are unpredictable.

Yes I do realised the latest tests results are quite unpredictable. I have since went back to using the Exit option. Seems to be working now (3 windows. Haven't try 4 yet)

It was quite predictable however previously for years. (killing by task manager) oh well i guess i will change my methods to whichever that works better.