Fire fox 50.1.0, Windows 10 I've got about 11 windows open with a total of about 400 tabs. One of these windows is such that the tabs are all screwed up, so I tried to do an Append Session for that window, but I got some stupid error like it couldn't find the data, and then trying to do the same thing later, when I select on a Crashed Session, there are no entries in the lower List control, whereas usually there are all the windows & tabs listed. I also try to do a Save Session, and similarly, there are no entries in the lower List control, and the Save Session button is disabled. I don't know what to do short of painstakingly saving every tab to Bookmarks and then opening them up.