[OS X TeX] Can typeset but cannot just save

[Alain Schremmer]

All of sudden, none of the many LaTeX files in a folder can be  
saved.  (TeX message) Yet,

(1 ) They can be typeset (and therefore saved)

(2)  If I move a file elsewhere, it still cannot be saved.

(2)  If I duplicate the file into another folder, the duplicate can  
be saved there. And once it is back in the main folder it can now be  
saved again.

So it is not a catastrophe but what am I missing?

Intrigued regards
--schremmer