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).

Make sure that your security software isn't protecting or restoring js files in the Firefox profile folder.

• http://kb.mozillazine.org/Profile_folder_-_Firefox

Deleting the sessionstore files seemed to help for now. I'll see how it goes but for now it's good.

Right so a day later and after closing firefox myself, it decided to bring up a firefox version from a few hours ago. Not as annoying as some of the stunts I've gotten but still.

My virus-scan and firewall are not doing anything to the js files in my profile folder.

Something I've noted is that every now and again, the sessionstore.js file refuses to back up; I check the last modified date and it's hours ago. I know that the interval value in about:config is still at its default 15000 value so I'm not sure why it decides to randomly misbehave.

You can try this startup setting:

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

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Firefox/Tools > Add-ons > Appearance).

• Do NOT click the Reset button on the Safe Mode start window.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

RE: Ancient Tabs restoring in secondary New Window

I had a similar yet not identical issue. For my Firefox v26, I had always had it set to auto Restore The Last Tab(s), and any new windows opened after that first window would open a single blank Tab. Recently a series of tabs from a restore long ago began arriving on the first window. Removing the session files described above helped clean that up. However, if I then used the File menu to Open A New Window, that second window opened all those ancient restored tabs. I also tried some about:config edits described in other articles without success, and then changed those values back once tested.

The fix for this particular situation was to edit the General tab in the Firefox Options (Tools menu > Options > General). I changed the Home Page entry to the Firefox default and I changed the start-up behavior ("When Firefox Starts") to not restore the last tabs, but just open the home page. Once everything was opening normally, with a plain homepage on the first window and the second window opening a blank tab, I then set my start-up back to restoring old tabs ("Show my windows and tabs from last time") and now it behaves as I wanted.

I hope that helps someone else. FYI