[RCU] Error upgrading from Version 0.1-beta2 to Version 0.1-rc1

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: http://dev.mysql.com/doc/mysql/en/error-messages-server.html

#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;

List info: http://lists.roundcube.net/users/