vertical bars and underscores between characters

[José Miguel Rivero Almeida]

--text follows this line--
This bug report will be sent to the Free Software Foundation,
not to your local site managers!
Please write in English, because the Emacs maintainers do not have
translators to read other languages for them.

Your bug report will be posted to the bug-gnu-emacs@gnu.org mailing list,
and to the gnu.emacs.bug news group.

In GNU Emacs 21.4.1 (i486-pc-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2007-06-19 on ninsei, modified by Debian
configured using `configure  '--build=i486-linux-gnu' 
'--host=i486-linux-gnu' '--prefix=/usr' '--sharedstatedir=/var/lib' 
'--libexecdir=/usr/lib' '--localstatedir=/var/lib' 
'--infodir=/usr/share/info' '--mandir=/usr/share/man' '--with-pop=yes' 
'--with-x=yes' '--with-x-toolkit=athena' 'build_alias=i486-linux-gnu' 
'host_alias=i486-linux-gnu' 'CFLAGS=-DDEBIAN -g -O2''
Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: es_ES.UTF-8
  locale-coding-system: utf-8
  default-enable-multibyte-characters: t

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

When I move the cursor backwards (with the left-arrow key or
with crtl-b) vertical bold-face bars appears after the character
at the previous cursor. Sometimes it is an bold-face underscore,
and sometimes everything is ok.
Then, if I move the cursor forwards, the vertical bars disappear,
and also most of the underscores. Anyway, with crtl-l the text
in is correctly displayed.
Also newlines produce an underscored first character in the new line.

Recent input:
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <menu-bar> <help-menu>
<report-emacs-bug>

Recent messages:
Loading 50a2ps (source)...done
Loading 50dictionaries-common (source)...
Loading debian-ispell...
Loading /var/cache/dictionaries-common/emacsen-ispell-default.el 
(source)...doneLoading debian-ispell...done
Loading /var/cache/dictionaries-common/emacsen-ispell-dicts.el 
(source)...done
Loading 50dictionaries-common (source)...done
Loading 50tramp (source)...done
For information about the GNU Project and its goals, type C-h C-p.
Loading emacsbug...done