> <!-- returns the last slide number -->
>    <xsl:template name="find.lastslide">
>      <xsl:value-of select="count(/xpresent/slide)"/>
>    </xsl:template>
> 
> <!-- creates an "slideX.html" string -->
> <xsl:template name="find.nextslide">
>      <xsl:variable name="next" select="position() + 1"/>
>      <xsl:variable name="last"><xsl:call-template
> 	name="find.lastslide"/></xsl:variable>
>      <xsl:choose>
>        <xsl:when test="$next &gt; $last">
> 	<xsl:variable name="result"><xsl:value-of 
> select="$last"/></xsl:variable>
>        </xsl:when>
>        <xsl:otherwise>
> 	<xsl:variable name="result"><xsl:value-of
> 	    select="$next"/></xsl:variable>
>        </xsl:otherwise>
>      </xsl:choose>
>      <xsl:value-of select="concat('slide',$result,'.html')"/>
>    </xsl:template>
> 

You should get a compile-time error saying that the $result variable is not
in scope at the point where you use it.

Complain to your XSLT processor vendor (or switch to a different processor),
and change your code to:

<xsl:variable name="result">
      <xsl:choose>
       <xsl:when test="$next &gt; $last">
	     <xsl:value-of select="$last"/>
        </xsl:when>
        <xsl:otherwise>
 	     <xsl:value-of select="$next"/>
        </xsl:otherwise>
      </xsl:choose>
</xsl:variable>
<xsl:value-of select="concat('slide',$result,'.html')"/>

Michael Kay