Errno 150 when adding foreign key (InnoDB)

# CocoaMySQL dump
# Version 0.5
# http://cocoamysql.sourceforge.net
#
# Host: localhost (MySQL 4.0.26-standard)
# Database: psyguide_development
# Generation Time: 2005-12-22 12:13:47 +0100
# ************************************************************

# Dump of table customers
# ------------------------------------------------------------

CREATE TABLE `customers` (
  `id` int(11) NOT NULL auto_increment,
  `name` varchar(100) default NULL,
  `plz` varchar(50) default NULL,
  `ort` varchar(50) default NULL,
  PRIMARY KEY  (`id`)
) TYPE=InnoDB;



# Dump of table orders
# ------------------------------------------------------------

CREATE TABLE `orders` (
  `id` int(11) NOT NULL auto_increment,
  `customer_id` int(11) default NULL,
  `bezeichnung` varchar(100) NOT NULL default '',
  `anzahl` int(11) NOT NULL default '1',
  PRIMARY KEY  (`id`),
  KEY `customer_id_idx` (`customer_id`)
) TYPE=InnoDB;

alter table orders add constraint customer_id_fk foreign key(customer_id) references customer(id);

Original - sql Code ALTER TABLE `test`.`orders` ADD CONSTRAINT `FK_orders_2_1` FOREIGN KEY `FK_orders_2_1` (`customer_id`) REFERENCES `customers` (`id`) ON DELETE RESTRICT ON UPDATE RESTRICT;

ALTER TABLE `test`.`orders` ADD CONSTRAINT `FK_orders_2_1` FOREIGN KEY `FK_orders_2_1` (`customer_id`)
    REFERENCES `customers` (`id`)
    ON DELETE RESTRICT
    ON UPDATE RESTRICT; 

drop database test;
create database test;
use test;

# CocoaMySQL dump
# Version 0.5
# http://cocoamysql.sourceforge.net
#
# Host: localhost (MySQL 4.0.26-standard)
# Database: psyguide_development
# Generation Time: 2005-12-22 22:01:35 +0100
# ************************************************************

# Dump of table _rails_standard
# ------------------------------------------------------------

CREATE TABLE `_rails_standard` (
  `id` int(11) NOT NULL auto_increment,
  `created_at` datetime NOT NULL default '0000-00-00 00:00:00',
  `updated_at` datetime NOT NULL default '0000-00-00 00:00:00',
  `lock_version` int(11) NOT NULL default '1',
  PRIMARY KEY  (`id`)
) TYPE=InnoDB;



# Dump of table members
# ------------------------------------------------------------

CREATE TABLE `members` (
  `id` int(11) NOT NULL auto_increment,
  `created_at` datetime default '0000-00-00 00:00:00',
  `updated_at` datetime default '0000-00-00 00:00:00',
  `lock_version` int(11) NOT NULL default '1',
  `nickname` varchar(40) default NULL,
  `first_name` varchar(20) default NULL,
  `last_name` varchar(20) default NULL,
  `email` varchar(60) default NULL,
  PRIMARY KEY  (`id`)
) TYPE=InnoDB;



# Dump of table internet_radios
# ------------------------------------------------------------

CREATE TABLE `internet_radios` (
  `id` int(11) NOT NULL auto_increment,
  `created_at` datetime NOT NULL default '0000-00-00 00:00:00',
  `updated_at` datetime NOT NULL default '0000-00-00 00:00:00',
  `lock_version` int(11) NOT NULL default '1',
  `url` varchar(100) default NULL,
  `playlist` varchar(100) default NULL,
  `member_id` int(11) NOT NULL default '0',
  PRIMARY KEY  (`id`)
) TYPE=InnoDB;


ALTER TABLE internet_radios ADD CONSTRAINT member_id_fk FOREIGN KEY member_id_fk (member_id)
          REFERENCES members (id)
          ON DELETE RESTRICT
          ON UPDATE RESTRICT;