Write about:support into your URL bar, press profile folder show folder and copy sessionstore.js and sessionstore.bak to somewhere else. Try renaming sessionstore.bak to sessionstore.js and put it into your profile folder and see what happens. If youre lucky and it hasnt already been overwritten by new info you'll get your old session back. Next time, do this immediately before the files get overwritten

thanks for your answer, unfortunately I have already restarted FF and cannot see the file sessionstore.bak. therefore there is no way to recover my tabs.  ;-(

Is this because sessionstore is a java file that I lost the session?? What do you suggest next time I want to update java without loosing my tabs?