Don't close Firefox. Please back up all your sessionstore files to a safe location for potential recovery/salvage operations. You can 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 and save a copy of all files whose names start with sessionstore to a safe location, such as your Documents folder. If not too much time has passed, we may be able to use them to recover your blank tabs. ---- Next, could you check the History menu for "Restore Previous Session"? This may appear on the application ("3-bar" menu) or on the menu bar. If "Restore Previous Session" is grayed out, then either Firefox has already loaded your previous session windows and tabs, or was unable to load the file. Check the History menu for the possibility of re-opening closed windows, and then closed tabs within each window. Anything recoverable? ---- The kinds of files you may find in among your sessionstore files are: * sessionstore.js: the windows and tabs in your currently live Firefox session (or, if Firefox is closed, your last session) * sessionstore.bak: the windows and tabs in your last Firefox session * sessionstore.bak-''datetime'': the windows and tabs in the Firefox session that was live at the time of your last update * sessionstore-1.js (or other numbered files): windows and tabs saved at a time when Firefox was unable to update the sessionstore.js file Could you take a look at what you have and the date/time of the various files to see whether you think any of them would have the missing windows and tabs?