jQuery Grid Plugin - jqGrid

I'm going through the "Creating your first grid" tutorial, and have set up the data, the index.html and example.php as suggested.  However, when I run the page, I get the grid layout, but no data inside it.  I have added al query to index.php as well:

$db = mysql_connect('localhost', 'myuser', 'mypassword') or die("Connection Error: " . mysql_error());
$myinv=mysql_select_db('mydatabase', $db) or die("Error connecting to db.");
$result = mysql_query("SELECT COUNT(*) AS count FROM invheader");
$row = mysql_fetch_array($result,MYSQL_ASSOC);
$count = $row['count'];
echo "Number of records: ".$count;

and this shows, below the empty grid:

Number of records: 2

as expected (there are two records in the db table), which suggests access to the db is OK.

The Firebug console gives the Response as:

<?xml version='1.0' encoding='utf-8'?><rows><page>1</page><total>1</total><records>2</records><row id
='2'><cell>2</cell><cell>2009-03-24</cell><cell>24.00</cell><cell>3.00</cell><cell>27.00</cell><cell
><![CDATA[watch re payment]]></cell></row><row id='1'><cell>1</cell><cell>2009-03-23</cell><cell>5.00
</cell><cell>1.00</cell><cell>6.00</cell><cell><![CDATA[first entry]]></cell></row></rows>

which seems to suggest that XML is making it back to the page, but is just not being displayed for some reason.

Any suggestions on what might be wrong?

I'm using Firefox 3.0.1 on openSUSE 10.2.

Thanks

Kevin