In GNU Emacs 21.3.2 (i386-pc-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2003-04-24 on raven, modified by Debian
configured using `configure  i386-linux --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 --without-gif'
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: C
  locale-coding-system: nil
  default-enable-multibyte-characters: t

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

I have loaded a utf-8 encoded text into the buffer, 
modified it, then tried to save it. Now emacs said the
following:

---------------
These default coding systems were tried:
  iso-latin-1-unix
However, none of them safely encodes the target text.

Select one of the following safe coding systems:
  utf-8 mule-utf-16-le mule-utf-16-be raw-text emacs-mule
  no-conversion
---------------

After that, I have entered C-g to escape from this function.
At this point, my original file has gone (and, there is no
recovery file yet). Anyway, if I quit without saving, the 
#filename# file's content isn't the same as the original (it
contains \201 bytes before non-ascii chars).

(Anyway, it is interesting why emacs does not recognize my 
txt as utf-8 text, and interprets it as iso-latin-1-unix...)

Attached I send the file gzipped which was loaded into emacs.

emacs started with: 'emacs test'

Recent input:
a DEL C-x C-s C-g C-x C-c n n o RET ESC x r e p o TAB 
r TAB RET

(If I would say 'yes' instead of 'no' at quit, emacs would generate a
'#test#' file where some bytes are preceded by \201 bytes.)

Recent messages:
Loading 50nowebm (source)...done
Loading 50w3 (source)...done
Loading 55doxymacs (source)...
Loading mule-util...done
Loading 55doxymacs (source)...done
For information about the GNU Project and its goals, type C-h C-p.
Loading view...done
byte-code: Quit
Making completion list...
Loading emacsbug...done

Regards:
Circum