Here's a quick script to reproduce the problem:

<?

	$x = array ("filename" => 	  array	(0 => "joe.doc", 1 => "ralph.doc", 2 => "maria.xls")
				, "size" => 	  array	(0 => "jbig", 1 => "rsmall", 2 => "mmed")
				, "modified" =>   array	(0 => "54", 1 => "32", 2 => "99")
				);

#	array_multisort ($x["modified"]);
	asort ($x["modified"]);
	reset ($x["modified"]);
	
	echo "<p><b>Values in x</b><br>";
	while (list ($key, $val) = each ($x)) {
	    echo "$key => $val<br>";
	}
	echo "<p><b>Values in filename</b><br>";
	while (list ($key, $val) = each ($x["filename"])) {
	    echo "$key => $val<br>";
	}
	echo "<p><b>Values in size</b><br>";
	while (list ($key, $val) = each ($x["size"])) {
	    echo "$key => $val<br>";
	}
	echo "<p><b>Values in modified</b><br>";
	while (list ($key, $val) = each ($x["modified"])) {
	    echo "$key => $val<br>";
	}

?>

Uncomment the "array_multisort" line and comment the "asort" line to witness the bug first hand.