Failed to load image

Hello all,

after switching from docbook-xsl-1.62.4 to docbook-xsl-1.67.2, I get 
errors of the form

Writing html/ch02.html for chapter(cha.SimpleDataTypes)
Failed to load image: Pictures/Dictionary.png
Failed to load image: Pictures/Dictionary.png
Failed to load image: Pictures/Dictionary.png
Failed to load image: Pictures/Dictionary.png

I did not change anything in my file structure or in my source document. 
The image file is still there, and the image is visible in the generated 
HTML page.

I include the image by

     <figure id="fig.Dictionary">
       <title>An English-German dictionary</title>
       <mediaobject>
         <imageobject  role="html">
           <imagedata  align="center" format="PNG" 
fileref="Pictures/Dictionary.png"/>
         </imageobject>
       </mediaobject>
     </figure>

The picture is here, in the subdirectory "html" where the HTML code is 
generated:

$ ll html/Pictures/Dictionary.png
-rw-r--r--    1 ziegler  Mehlhorn     6147 Oct 15  2003 
html/Pictures/Dictionary.png

Before 1.67.2, I did not get this error message.

Can I just ignore it?

Greetings,
Joachim

-- 
Joachim Ziegler                       Stuhlsatzenhausweg 85
Max-Planck-Institut für Informatik    66123 Saarbrücken, Germany
Email:           Tel.: (+49) 0681 9325-127
"I never wanted to be a computer scientist. I wanted to be... a lumberjack!"