Was Firefox running when that battery got flat?

It is possible that the file sessionstore.js got corrupted if that was the case.

If you see any sessionstore files with a number (sessionstore-##.js) in the Firefox Profile Folder then make a backup copy elsewhere and rename the file to sessionstore.js with Firefox closed.

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

• Help > Troubleshooting Information > Profile Directory: Open Containing Folder

"Was Firefox running when that battery got flat?" Yes.

"If you see any sessionstore files with a number (sessionstore-##.js) in the Firefox Profile Folder..." There's only a file called sessionstore.js.

"http://kb.mozillazine.org/Session_Restore" says to set "When Firefox starts" to "Show my windows and tabs from last time". I have Firefox 4, and this option isn't there.

In Firefox 4 you can find that setting via Firefox > Options > General > When Firefox starts.

That session is probably lost if you can't access the previous session or have recently closed tabs or windows in Firefox > History

If you still see empty tabs then you need to delete sessionstore.js and sessionstore.bak in the Profile Folder
(this line got lost somehow in my above post, but should have been there)

Thanks.

"In Firefox 4 you can find that setting via Firefox > Options > General > When Firefox starts." This option isn't there, this being due to having the Tab Mix Plus add-on. I've now set it to use Firefox's built-in Session Restore feature, and will see it how that goes.

I don't have a sessionstore.bak file.