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

App tabs and Tab Groups (Panorama) are stored as part of the session data in the file sessionstore.js in the Firefox Profile Folder

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

Make sure that you do not use Delete browsing, search and download history on Firefox to clear the "Browsing History"

Thanks for this ... really so obvious .. don't know how I missed this .. thanks - Andy

I went to options and startup and saw that I had selected the correct thing and saved but it still won't save my tabs. Grrrrrr