Sebastien Vauban writes:
> These allow me to do everything I want (I'm even admin of my machine).

Just as a comment, being admin does not necessarily mean that you can do
anything, only that you can elevate your rights so that you can
eventually do it.  Windows has quite an elaborate system for permissions
(and revocations thereof) in the file system and the point of lots of
those is precisely to restrict was an admin can do by default.

> Absolutely. You pinpoint a real un-understandable thing (at least, for now)...

While I still don't understand how this is happening exactly, I've
re-written the functions in question to work off temporary buffers,
which only runs into the problem of non-writability at the very end when
the file is to be saved and should then ask for confirmation.  At that
point it should be possible to see what is going on.