Any file can be corrupted. Malware, blackouts, brownouts, not shutting down the computer properly, not shutting down the program properly . . . .

I appreciate the response.

I have not seen a corrupt file in years.

What is different about Firefox profiles that only those files would become unusable? It's gotta be a Firefox bug, triggered by something as yet unknown.

I have never heard of that ever happening before, and never had that happen to me either. My guess is that the changes made for Firefox 68 with regards to how Profiles are handled for or with the installs.ini file which sits in the same folder as the profiles.ini file which is probably connected to what happened for you.

My installs.ini file contains this:

[DD4B00EEFFB46EA8]
Default=Profiles/4htwhpvs.08-25-19_New-for-YouTube_channels-transfer
Locked=1

That appears (to me) to be a 2nd "lock" for a Profile and separate from the parent.lock file that is usually what "gets stuck" and causes issues in the past. Or possibly the cause for you. I have seen a few users complaining about a "locked Profile" since Firefox 68 was released but not related to how you described your issue with profiles.ini.

Overall the changes have to do with Firefox 68-plus versions being able to "pin" or "assign" a Profile to a specific Firefox program files installation, where prior each Profile was not "pinned" to a specific Firefox installation / version number.

It is possible that there was a permission problem (read/write/owner) with profiles.ini

cor-el said

It is possible that there was a permission problem (read/write/owner) with profiles.ini

I don't have a way to see what the permissions were, but that is a great guess. Kinda wish I had thought of it...

...and, come to think of it, I remember doing something that affected all the permissions on everything in my home directory and its descendants. On a Mac, that includes the Library directory containing the profiles.ini. I think what I did was issue a command to set every file to a certain permission (775). At the time, I recognized the potential for problems. I just switched to FIrefox around the same time (away from politically-biased (and lying about it) Google - can you believe that company says they are not biased because they are determining what reality is, they are biased only if reality is biased -- that company is the biggest threat to this country in my lifetime (born 1960) anyway, I digress)

I am bonehead for not remembering I had changed permissions. I think your question likely aims at the culprit. Thanks for mentioning it.