For some reason a few days ago after closing Bookmarks sidebar a few times to view full-window video, I re-enabled the sidebar as always (both with clicking the icon and CTRL + B, and they came back. Now, EVERY time I open FF (using W10), the sidebar will NOT show up unless I click CTRL + B or the icon on the bar on top of the window. I have installed nothing. Nothing crashed. FF is up to date. I refreshed it. I uninstalled it. I REINSTALLED it from scratch. I performed a system restore FOUR TIMES, yet cannot get back my sidebar when opening FF. Further, when I open the sidebar with CTRL + B, the column is VERY narrow and I have to widen it. So it appears that FF cannot remember the setting for the sidebar and defaults to a skinny one when activated. I ran troubleshooting mode and YES! The sidebar works as it should and opens with a new browser opening...ONCE. I disabled/deleted ALL extensions (I only use four), but I have not changed any parameters of FF or my system in general for this to be happening. I've checked EVERY setting in FF over and over, trying everything that could be relevant. Now what? After reinstalling I'm left with the same problem. What can I do? I cannot live with NO sidebar on startup. Oh and the silly Bookmarks bar DOES work, but I don't use it...it's stupid and I don't like the look or placement of it. This problem is SIDEBAR ONLY.