I normally have Firefox set up to have 5 pinned tabs and 2 or 3 saved tabs from the previous session of Firefox. Since I updated to version 19 FF, I lose 1 pinned tab each time FF is started. I have tried the fixes suggested regarding the sessionstore.js file corruption issue, checked to make sure Firefox "Will Remember history" is selected, used the File>Exit to quit FF. Each time I start up Firefox, I am missing a pinned tab (not all of them, just one). I started with 5 and I can exit, then start up FF and only 4 pinned tabs are opened. Repeat, and only 3 are opened, etc. If I have a normal tab opened when I exit, it's saved & opens the next time FF starts, so it seems opened tabs are being saved, but the pinned tabs are being closed. Also, it's always the second pinned tab that is lost (counting from the left). When there is only one pinned tab left, the next time I restart FF, one normal tab is closed. Each start after that will close another normal tab until only one pinned tab is left (the left most pinned tab). I haven't tried restarting FF with only the single pinned tab, but the bottom line is that I lose 1 saved tab each time I exit and re-start FF. Anyone else see this behaviour or have suggestions to fix?