xsl:attribute vs "expected comment or PI"?

I'm baffled. Why is this not working? The error I'm getting is "expected
comment or processing instruction". The problem is somewhere within the
second xsl:attribute ... if I take it out, no error. I've tried switching
the two xsl:attributes around, I've tried jamming it all onto one line, I've
tried taking the other xsl:attribute out ... no luck.

<xsl:template match="fmp:FMPXMLRESULT">
<ul>
<xsl:for-each select="fmp:RESULTSET/fmp:ROW">
 <li>
  <a>
   <xsl:attribute name="href">authors-<xsl:value-of
select="fmp:COL[1]/fmp:DATA[1]"/>.html</xsl:attribute>
   <xsl:attribute name="title">
    <xsl:value-of select="fmp:COL[2]/fmp:DATA[1]"/> author
    <xsl:if test="fmp:COL[2]/fmp:DATA[1]!='1'">s</xsl:if>,
    <xsl:value-of select="fmp:COL[3]/fmp:DATA[1]"/> article
    <xsl:if test="fmp:COL[3]/fmp:DATA[1]!='1'">s</xsl:if>
   </xsl:attribute>
   <xsl:value-of select="fmp:COL[2]/fmp:DATA[1]"/></a></li>
</xsl:for-each>
</ul>
</xsl:template>

The input data looks like this:

<FMPXMLRESULT xmlns="http://www.filemaker.com/fmpxmlresult">
<RESULTSET FOUND="345">
<ROW MODID="6" RECORDID="24">
    <COL><DATA>A</DATA></COL>
    <COL><DATA>18</DATA></COL>
    <COL><DATA>15</DATA></COL>
</ROW>
<ROW MODID="6" RECORDID="25">
    <COL><DATA>B</DATA></COL>
    <COL><DATA>18</DATA></COL>
    <COL><DATA>15</DATA></COL>
</ROW>
</RESULTSET>
</FMPXMLRESULT>