Well, I managed to get something working last night but then I got too tired to try and figure out just what the differences were between your code and mine. However, I did note that one thing in particular seemed to make a difference. The top line of your XML file should read something like this:
The following is what I used for the stylesheet:
<?xml-stylesheet type="text/xsl" href="sort.xsl"?>
One thing that I find odd though is that it doesn't appear to sort those numbers in ascending order, which I found very odd. Perhaps someone could explain just how this type of sort works?
<xsl:output method="xml" version="1.0"
<xsl:sort select="start" data-type="number" order="ascending"/>
<xsl:value-of select="start"/><br />