It may or may not be helpful. With that out of the way...

--> Open up about:config

--> Click on "I will be careful, I promise"

--> In the filter bar, type "browser.startup.page"

--> Right click on the displayed entry and change the value to 2 (if it is not already set to 3)

The value three means that "The previous browser session would be opened"

Didnt work. It was already set to 3, so i set it to 2. Which just opens a new tab. So i set it to 3 again, and it just opened a new window like before

Your previous tabs will not re-open or be available to re-open when starting Firefox if:

• your previous session was in Private Browsing mode; see --> http://support.mozilla.org/en-US/kb/Private+Browsing
• you use Clear Recent History (Firefox button > History > Clear Recent History or Tools > Clear Recent History); see --> https://support.mozilla.org/en-US/kb/Clear%20Recent%20History#w_how-do-i-clear-my-history
• you clear History automatically when closing Firefox; see --> https://support.mozilla.org/en-US/kb/Clear%20Recent%20History#w_how-do-i-make-firefox-clear-my-history-automatically

NOTE: Your third-party Plugins (Add-ons > Plugins) are not in the "Application Basics" (Troubleshooting Information) in the "More system details" of your original post. Third-party Plugins are categorized separately in "Installed Plugins" under "More system details". You should review but not change the Plugins as detected automatically by the software on this forum when posting a question.

If you problem still exists after checking the above, the problem could be caused by one or more of your Extensions or Plugins:

• See --> Troubleshooting extensions and themes
• See --> Troubleshooting plugins
• See --> Basic Troubleshooting

If this reply solves your problem, please click "Solved It" next to this reply when signed-in to the forum.

It is possible that there is a problem with the files sessionstore.js and sessionstore.bak in the Firefox Profile Folder.

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: Open Containing Folder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

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

See also:

• http://kb.mozillazine.org/Session_Restore
• http://kb.mozillazine.org/sessionstore.js
• http://kb.mozillazine.org/Multiple_profile_files_created

Im going to ignore SafeBrowser since it's either automated or can't read. Also my plug-ins are basic stuff which havent updated recently enough to have caused this. Stuff like flash player, facebook video calling, java, etc.

cor-el, I closed firefox, deleted those files and it's still not working, you got anything else?

You can do a check for problems with the prefs.js file.

• http://kb.mozillazine.org/Preferences_not_saved
• https://support.mozilla.org/kb/Preferences+are+not+saved

Well it seems that the problem fixed itself. I dont know what happened. But when I opened Firefox after a couple of hours of leaving it closed, it opened two different windows. One from last night and a brand new one. Closed both and now its working fine. Firefox probably didnt close properly last night. Maybe