If you go to the History menu, is "Restore Previous Session" available? You can check that either: * "3-bar" menu button > History * classic menu bar: History If it's grayed out, then that's a bad sign. Do not close Firefox. First, try to rescue the following files: Open your current Firefox settings (AKA Firefox profile) folder using either * "3-bar" menu button > "?" button > Troubleshooting Information * (menu bar) Help > Troubleshooting Information * type or paste about:support in the address bar and press Enter In the first table on the page, click the "Show Folder" button. In the window that launches, scroll down: (1) Double-click into the '''sessionstore-backups''' folder. Anything from the relevant date/time? If so, copy it to a safe location such as your Documents folder or Desktop. (2) Back at the main level, scroll down to the sessionstore file(s). Same question. If so, copy it to a safe location such as your Documents folder or Desktop. ---- The kinds of files you may find among your sessionstore files are: * sessionstore.js and recovery.js: the windows and tabs in your currently live Firefox session (or, if Firefox is closed, your last session) * recovery.bak: a backup copy of recovery.js * previous.js: the windows and tabs in your last Firefox session; sessionstore.bak for pre-33 versions of Firefox * upgrade.js-''build_id'': the windows and tabs in the Firefox session that was live at the time of your last update; sessionstore.bak-''datetime'' for pre-33 versions of Firefox If you come up with something promising, you may be able to have Firefox use it for your next session (details if relevant).