There are several questions that seem similar, e.g., http://apple.stackexchange.com/questions/63925/textedit-shows-dialogs-about-not-having-permission-to-open-any-files, but they're not exactly the same and none of the suggested fixes work.

For more than a month, I've been using the "re-open windows on login" option to keep a few Textedit files easily accessible.  No problem noted with an occasional save or opening a new one.

But today, I cannot save any of them nor open any new ones in my home directory.  OS 10.12.1

 - There are no ACLs in the entire /Users tree.
 - There are no extended attributes on the file I am trying to open
 - There are no extended attributes on ~ nor on /Users
 - Windows I want to save have not yet been, so can't have extended
   attributes
 - 'sudo chmod -R u+r,u+w /Users' did not fix it
 - 'sudo rm -rf `(user)/Library/Autosave\ Information' did not fix it
 - 'touch' created the file, and 'vim' can open, edit, and save it.
 - The school has a service which monitors the LAN for suspicious traffic.

There are some recent unusual events which don't seem capable of causing this, but just in case:

 - A post-graduate student's MacBook Air failed right before her
   comprehensive exams.  She's blind, so learning Windows overnight was
   not an option
 - I created a non-admin account for her on my MacBook Pro (MBP), help her set up VoiceOver, copied in her ~/Documents and a few other important items, and changed the UID (she was 502 on hers and 504 on mine)
 - Exams took three days (long difficult essay questions) during which she probably closed the lid to 'sleep' between tests rather than log out or shut down.
 - She logged out and handed me the MBP around ten hours ago.
 - I updated MalwareBytes and a scan found and removed OSX.Genieo (which AFAIK has to do with adware, not home permissions.  The previous version never found anything and I suspect wasn't even scanning (it took less than a half-second to say that it found nothing in over 500GB!)

Any ideas on a fix or a cause?