Save buffer (SGML mode) sporadically appends null characters

[Claude Schildknecht]

The save-buffer (C-x C-s) command in SGML mode sporadically appends
null characters to the saved file.

To recover the file I have to create a new buffer in SGML mode (C-x
C-f filename) and then copy the region from the file having null
characters and yank it into the newly created buffer.

I tried to change the emacs configuration, in particular the coding
system without success. I did not found any posting corresponding to
such problem.

I'm using emacs 21.3.1 on Windows NT 4 and the psgml package 1.2.5

Extract from my .emacs file

(add-to-list 'load-path (expand-file-name "~/psgml-1.2.5"))

(set-language-environment 'Latin-1)

(require 'psgml) 

(autoload 'sgml-mode "psgml" "Major mode to edit SGML files." t)
(autoload 'xml-mode "psgml" "Major mode to edit XML files." t)

;; here we set the syntax color information for psgml
(setq-default sgml-set-face t)
;;
;; Faces.
;;
(make-face 'sgml-comment-face)
(make-face 'sgml-doctype-face)
(make-face 'sgml-end-tag-face)
(make-face 'sgml-entity-face)
(make-face 'sgml-ignored-face)

and so on

I would appreciate any help / hint to solve my problem.

Many thanks

Regards,

Claude