bug#13298: 24.3.50; Cannot write backup file; backing up in ~\.emacs.d\%backup%~

[Eli Zaretskii]

> Date: Sat, 29 Dec 2012 15:25:54 +0400
> From: Dmitry Gutov <dgutov@yandex.ru>
> CC: 13298@debbugs.gnu.org
> 
> >> 1. emacs -Q
> >> 2. M-x ido-mode OR M-x recentf-mode (either one's fine)
> >> 3. C-x C-c
> >> 4. See the message above and a new directory in ~\.emacs.d\ (if it
> >> didn't exist already).
> >
> > Do you see a similar message when you edit a file and save it?
> 
> I don't (tried with non-vc-controlled files, to be sure).
> 
> But I see it when I quit gnus, by the way. Twice.

Can you step with a debugger (e.g., Edebug) through
backup-buffer-copy, and see why it errors out?  My crystal ball says
it happens because of set-file-extended-attributes, in which case
please tell what is the value of extended-attributes argument passed
to backup-buffer-copy.

Also, do you see any other error messages in *Messages* when this
happens?