PNGs not appearing in PDF (appearing fine in HTML)

[Nathan Bailey <nathan.bailey@monash.edu>]

docbook2html -u myfile.docbook generates an HTML file that includes my  
pictures.
docbook2pdf -u myfile.docbook generates a PDF with only the text  
alternates/captions/etc.

I have tried a variety of ways of specifying the picture, drawing on  
similar reports on this list archive to no avail. I've looked at Nik  
Clayton's Makefiles but am not currently using them. I suspect the  
stylesheets reflect his suggested changes now?
Here's an extract from my docbook file; foo.png is in the current  
directory.

<para>
<emphasis>(style sheet leaves this page blank)</emphasis>
<figure>
    <title>An Image</title>
    <mediaobject>
       <imageobject>
          <imagedata fileref="foo.png" align="center" width="100%"  
scalefit="1"/>
       </imageobject>
    </mediaobject>
</figure>

<mediaobject>
  <imageobject>
    <imagedata fileref="foo"/>  <!-- Filename, without extension -->
  </imageobject>

  <textobject>
    <phrase>Another image</phrase>
  </textobject>
</mediaobject>

<mediaobject>
   <imageobject>
     <imagedata fileref="foo.png" format="PNG"/>
   </imageobject>
   <textobject>
     <phrase>Desk with empty email inbox and paper in-tray</phrase>
   </textobject>
   <caption>
    <para>
    Processed!
    </para>
   </caption>
</mediaobject>


docbook2pdf is a shell script with the single line:
jw -f docbook -b pdf "$@"

jw is a 'jade wrapper' which runs openjade, which reports:
openjade:I: "openjade" version "1.3.2"
openjade:I: "OpenSP" version "1.5.1"

docbook-dsssl-nwalsh's VERSION is 1.79 (this may be fink's version?  
the last date in the subdir's change logs is lib/ChangeLog:2004-10-24   
<petere78@users.sourceforge.net>)
I'm running docbook on a MacBook Pro with Mac OS X 10.5.8.

thanks for any help you can provide!
Nathan
PS: I also have another figure with two imageobjects, 'something  
else.png' and 'something else.eps'. The former works ok in HTML, but  
the later confuses TeX, I think (doesn't handle spaces?) "else.eps"  
appears in the text of the resulting PDF, with an error in myfile.log  
that actually references the full filename, interestingly enough...  
(and indicates that .eps isn't a supported format)