No way to tell with that information. I would suggest you do some error logging with some meaningful debug output to help you determine which queries are not working.
$sql2= "update friend_user_photo set comments=comments + 1 WHERE auto_id='$photoid'";
$result = executequery($sql);
if(!$result)
{
error_log("Query failed: [$sql2] " . mysql_error() . "\n", 3, __FILE__ . ".errors");
}
elseif(mysql_affected_rows() == 0)
{
error_log("Query worked but no rows updated [$sql2]\n", 3, __FILE__ . ".errors");
}
}