Ok, so atleast now you know there is a problem when sending your query. might want to check your SQL statement.
Change this:
#
//Now we search for our search term, in the field the user specified
#
$data = mysql_query("SELECT * FROM users WHERE upper($field) LIKE'%$find%'");
to:
//Now we search for our search term, in the field the user specified
$sql = "SELECT * FROM users WHERE upper($field) LIKE'%$find%'";
echo $sql;
$data = mysql_query($sql) or die(mysql_error());
This way you can see exactly what is being sent to the database.