New to the list. I am trying to upgrade from from Version 0.1-beta2 to Version 0.1-rc1

and am receiving the following error when running the mysql.update.sql script. Can someone please tell

me how to fix this. thanks!

SQL query:

ALTER TABLE `messages` DROP `body` ,
DROP INDEX `cache_key` ,
ADD `structure` TEXT,
ADD UNIQUE `uniqueness` ( `user_id` , `cache_key` , `uid` ) ;

MySQL said:

#1062 - Duplicate entry '4-INBOX.msg-390' for key 2

and here is the script 
that was supplied to upgrade:

-- RoundCube Webmail update script for MySQL databases
-- Updates from version 0.1-beta and 0.1-beta2

ALTER TABLE `messages`
DROP `body`,
DROP INDEX `cache_key`,
ADD `structure` TEXT,
ADD UNIQUE `uniqueness` (`user_id`, `cache_key`, `uid`);

ALTER TABLE `identities`
ADD `html_signature` tinyint(1) default 0 NOT NULL;

-- Uncomment these lines if you're using MySQL 4.1 or higher
ALTER TABLE `users`
DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci,
CHANGE `username` `username` VARCHAR( 128 ) CHARACTER SET utf8 COLLATE utf8_
general_ci NOT NULL,
CHANGE `alias` `alias` VARCHAR( 128 ) CHARACTER SET utf8 COLLATE utf8_genera
l_ci NOT NULL;