DOCBOOK-APPS: xsl-fo: title page customization

[Bernd Kuemmerlen <bkuemmer at gmx dot net>]

Hello there,

sorry if this might be a newbie question, but I am very new to the world 
of xsl.

I would like to customize the title pages of our pdf documents using the 
method described in 
<http://www.sagehill.net/xml/docbookxsl/HtmlCustomEx.html#HTMLTitlePage> 
and 
<http://www.sagehill.net/xml/docbookxsl/PrintCustomEx.html#PrintTitlepageSpecfile>

My problem is that the stylesheet I create with

xsltproc --output fo/mytitlepages.xsl template/titlepage.xsl 
fo/titlepage.templates.xml

(for testing purposes I just tried to use the provided 
titlepage.templates.xml) has a lot of empty namespace prefix 
declarations like

<fo:block xmlns:fo="http://www.w3.org/1999/XSL/Format"; xmlns:ns1="" 
xsl:use-attribute-sets="article.titlepage.recto.style" 
ns1:keep-with-next="always" ns1:font-size="24.8832pt" 
ns1:font-weight="bold">

the fo generation from a DocBook XML file using xsltproc gives lots of 
errors about "Empty namespace name for prefix ns...":

 xsltproc --catalogs --output ./fo/job.fo \ 
/raid/1/projects/ilab/Documentation/lib/xml/xsl/docbook/mevis/fo.xsl job.xml
/raid/1/projects/ilab/Documentation/lib/xml/xsl/docbook/fo/mytitlepages.xsl:152: 
error: Empty namespace name for prefix ns1
le" ns1:keep-with-next="always" ns1:font-size="24.8832pt" 
ns1:font-weight="bold

       ^
/raid/1/projects/ilab/Documentation/lib/xml/xsl/docbook/fo/mytitlepages.xsl:166: 
error: Empty namespace name for prefix ns2
="article.titlepage.recto.style" ns2:space-before="0.5em" 
ns2:font-size="14.4pt

       ^

and the subsequent processing of the FO with XEP also fails with an 
error related to the prefix:

xep.sh -fo ./fo/job.fo -out ./pdf/job.pdf
(document
(validate SAX parsing errors encountered no such prefix "ns15"

What is the problem here? Is there any option to xsltproc I must set?
The versions I am using are

xsltproc --version
Using libxml 20501, libxslt 10024 and libexslt 715
xsltproc was compiled against libxml 20501, libxslt 10024 and libexslt 715
libxslt 10024 was compiled against libxml 20500
libexslt 715 was compiled against libxml 20500

and

docbook-xsl-1.60.1

Thanks for any help
	Bernd