xsl namespace problem

Hi

	My stylesheet is not working when I add a namespace.  Can you help
me?

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="1.0"
xmlns:aco="http://www.org/TRIP2004A/01">
  <xsl:output method="xml"/>
  <xsl:template
match="aco:/GetProductOptionsResponse/DetailedProduct/ProductOptionGroup/Pro
ductOption">
     <xsl:copy>
       <xsl:apply-templates>
         <xsl:sort data-type="number" select="aco:@netAmount"
order="ascending"/>
       </xsl:apply-templates>
     </xsl:copy>
  </xsl:template>

  <xsl:template match="*">
     <xsl:copy>
        <xsl:apply-templates/>
     </xsl:copy>
  </xsl:template>
</xsl:stylesheet>


<GetProductOptionsResponse xmlns="http://www.accovia/TRIP2004A/01">
    <Header language="en" version="5.1.0"/>
	<DetailedProduct availabilityStatus="available">
	<ProductOptionGroup description="AVO SOUS FORFAIT HTL">
	    <ProductOption availabilityStatus="available">
                <NetPrice currency="EUR" netAmount="2.27"
                    priceReferenceID="HTLAVO13XAAX"
quantity="1">W</NetPrice>
                <NetPrice currency="EUR" netAmount="1.09"
                    priceReferenceID="HTLAVO13XAAX"
quantity="1">M</NetPrice>
		<TravelerPrice age="10" travelerId="003">
                    <PriceSummary baseAmount="0.00"/>
		</TravelerPrice>
            </ProductOption>
        </ProductOptionGroup>
    	</DetailedProduct>
</GetProductOptionsResponse>

	I would like also to copy all attributes in the XML output.  I want
the same output XML as my input XML but with the NetPrice sorted by
netAmount.

Thanks for your help
Stephane