Firefox is having a problem processing the file. You might need to just salvage the URLs out of it if Firefox can't read it correctly. Do you know which session history file you restored, for example, the standard previous.js file versus a file saved by the Session Manager extension? ''Note: if you do not see .js extensions on session history file names, set Windows to show all file extensions so you can accurately identify files and more easily rename them: [http://windows.microsoft.com/en-us/windows/show-hide-file-name-extensions http://windows.microsoft.com/en-us/windows/show-hide-file-name-extensions].'' I recommend making a copy of the file on the desktop and renaming the copy to '''losttabs.txt''' (or another .txt file). Open losttabs.txt in a Firefox tab. Then open the Web Console in the lower part of the tab using either: * Ctrl+Shift+k * Developer menu Then paste the code from the following post into the space at the bottom of the Web Console and press Enter to run it, and that should extract a list of URLs that were in the file: https://support.mozilla.org/questions/1085742#answer-786810