superscripts in page headers

I am trying to use the contents of bookinfo/title in the page header.
This title contains the subelement: "<superscript>&reg;</superscript>".
I'm specifying this with the following in my "
header.content" template:

<xsl:when test="$sequence = 'even' and $position = 'left'">  
    <xsl:value-of select="//bookinfo/title"/>
</xsl:when>

The problem is that the "superscript" is ignored and the "registered"
symbol is on the baseline and too large.

For the right header I use the following:

<xsl:when test="$sequence = 'odd' and $position = 'right'">

        <xsl:apply-templates select="." mode="object.title.markup"/>
</xsl:when>

On the TOC pages this pulls in the bookinfo/title, but here the "&reg;"
IS superscripted.

These are obviously taking different pathways through the templates,
but is there any way to get the superscripting to work in the first ?

My environment:
    docbook-xsl-1.73.2 (but get the same results with 
1.72.0)
    FOP 0.94
    Docbook 4.12
    xalan-j_2_7_0
    Windows XP

Any help is appreciated.

Thanks.