Are you using Delete browsing, search and download history on Firefox to clear data if you close Firefox?

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

For the record, under Option I had enabled "Show my windows and tabs from last time."

However, when I open my Firefox Profile Folder (by inserting %APPDATA%\Mozilla\Firefox\Profiles in the Windows 7 search box) I don't see the file sessionstore.js. (I presume it should be between secmod.db and signons3.txt.)

I fiddled about some more and appear to have solved the problem. (I deleted TabMixPlus and re-downloaded Firefox 4, neither of which had any impact. Then I went to Options>>Privacy and clicked Remember history.

Now, Firefox is restoring the tabs that were open when I closed and the Panorama tab groups are also appearing.

Thanks for pointing me in the right direction.

But I still don't see the sessionstore.js file.

Windows may hide the .js file extension so you may only see a sessionstore file.

If Tab Mix Plus uses it own implementation of session store then that may interfere with saving App tabs and Tab groups in sessionstore.js, so you can try to disable that feature in TMP. Also make sure to use the latest development build of TMP.

• http://tmp.garyr.net/forum/viewforum.php?f=3