[xsl] Newbie problem: namespace breaks key

[Robert Carter <rcarter0@xxxxxxxxxxxxx>]

Is there a reason why <xsl:key> would break when a namespace is added  
to the source document?

Example: I begin with this input xml:
----
<?xml version="1.0" encoding="UTF-8"?>
<FMPDSORESULT>
    <ROW rowid='1'>
        <ITEM type="main">Krazy Kat</ITEM>
        <ITEM type="other">Ignatz</ITEM>
        <ITEM type="other">Offisa Pup</ITEM>
    </ROW>
    <ROW rowid='2'>
        <ITEM type="main">Superman</ITEM>
        <ITEM type="other">Lex Luther</ITEM>
        <ITEM type="other">Lois Lane</ITEM>
    </ROW>
</FMPDSORESULT>
----

Then apply this transformation:
----
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform";  
version="1.0">
    <xsl:output method="xml" indent="yes"/>

<xsl:key name="item_match" match="ITEM" use="@type"/>

    <xsl:template match="ROW">
        <xsl:variable name="thisRow" select="@rowid"/>
    <mainCharacter>
        <xsl:value-of select="key('item_match', 'main')[position()= 
$thisRow]"/>
    </mainCharacter>
    </xsl:template>

    <xsl:template match="text()"/>

    <xsl:template match="/">
        <strips>
        <xsl:apply-templates select="FMPDSORESULT"/>
        </strips>
    </xsl:template>
</xsl:stylesheet>
----

I get the following output:
----
<?xml version="1.0" encoding="utf-8"?>
<strips>
   <mainCharacter>Krazy Kat</mainCharacter>
   <mainCharacter>Superman</mainCharacter>
</strips>
----

All well and good. Now, I add a namespace to the input XML, so that  
the first two lines read:
----
<?xml version="1.0" encoding="UTF-8"?>
<FMPDSORESULT xmlns="http://www.filemaker.com/fmpdsoresult";>
----
...and I make the appropriate changes in my XSLT, adding the prefixes  
where I reference an element, so that my transformation now looks  
like this:
----
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform";  
version="1.0" xmlns:fm="http://filemaker.com/fmpdsoresult"; exclude- 
result-prefixes="fm">
    <xsl:output method="xml" indent="yes"/>

<xsl:key name="item_match" match="fm:ITEM" use="@type"/>

    <xsl:template match="fm:ROW">
        <xsl:variable name="thisRow" select="@rowid"/>
    <mainCharacter>
        <xsl:value-of select="key('item_match', 'main')[position()= 
$thisRow]"/>
    </mainCharacter>
    </xsl:template>

    <xsl:template match="text()"/>

    <xsl:template match="/">
        <strips>
        <xsl:apply-templates select="fm:FMPDSORESULT"/>
        </strips>
    </xsl:template>
</xsl:stylesheet>
----
my result XML comes out empty. The problem seems to be that the  
<key>  function results in an empty node set after the namespace  
prefixes are added.

Is this due to some newbie mistake on my part, like not adding the  
prefix in some place where I should have? Or does <xsl:key> have a  
problem with namespaces?

Thanks--
Robert Carter

(Oxygen 8.2, XSL 1.0, Saxon 6.5.5)