Update: something is seriously screwed up with this new FF 46 version. Does exactly the same thing in my 10.9, where it's not supposed to be deprecated.

Not EOL, just very screwed up.

https://www.mozilla.org/en-US/firefox/46.0/system-requirements/

See "Intent to deprecate: MacOS 10.6-10.8 support":

• https://groups.google.com/forum/#!topic/mozilla.dev.platform/gXZj0rQWEfI

You can try the Firefox 45.1.0 esr version. Firefox 45.1.0 ESR:

• https://www.mozilla.org/en-US/firefox/organizations/all/

• https://www.mozilla.org/en-US/firefox/45.1.0/releasenotes/
• https://www.mozilla.org/en-US/firefox/45.0/system-requirements/
• https://www.mozilla.org/en-US/firefox/organizations/system-requirements/

(fixed system-requirements link)

cor-el said

See "Intent to deprecate: MacOS 10.6-10.8 support":

• https://groups.google.com/forum/#!topic/mozilla.dev.platform/gXZj0rQWEfI

Which does not say that support for OSX 10.6, 10.7, 10.8 has indeed ended as of Firefox 46.0 and the OP is having same issue with OSX 10.9 also.

Could you confirm the sidebars and Bookmarks Toolbar problems in Firefox's Safe Mode? In Safe Mode, Firefox temporarily deactivates extensions, hardware acceleration, and some other advanced features to help you assess whether these are causing the problem.

If Firefox is not running: Hold down the option/alt key when starting Firefox. (On Windows, hold down the Shift key.)

If Firefox is running: You can restart Firefox in Safe Mode using either:

• "3-bar" menu button > "?" button > Restart with Add-ons Disabled
• Help menu > Restart with Add-ons Disabled

and OK the restart.

Both scenarios: A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any improvement?

Decided that it's probably a corrupt profile. Switched instead to the 45.1.0 ESR, which is working fine. This way, I don't have to create a new profile and the huge amount of work that would entail for me (did one not that long ago, was several days' work) and still get the latest security patches, which is really all I care about. Not the latest UI, which just keeps getting junkier and junkier. Mostly change for the sake of change.

Should the ESR start getting obviously funky in some way, I'll have to create a new profile then. Right now, I don't have any desire or energy to go through all that again.

By the time the 45 ESR is EOL, FF will be a completely different animal, as Mozilla tries to turn it into a Chrome clone, and I may not have any use for it then at all.

Profile corruption is one major downside of Firefox.

So why didn't they add version-checking to Firefox 46 so that I would get a warning when I downloaded the update?

cor-el said

Firefox 45.1.0 ESR:

• https://www.mozilla.org/en-US/firefox/organizations/all/

• https://www.mozilla.org/en-US/firefox/45.1.0/releasenotes/
• https://www.mozilla.org/en-US/firefox/organization/system-requirements/

FYI, the first link works, but the "release notes" link leads to a page to download FF 46.0 and the "system requirements" link gives a 404 error.

Sorry, there is an 's' missing in organizations in the Release Notes:

• https://www.mozilla.org/en-US/firefox/organizations/system-requirements/