Решение здесь
http://www.phoca.cz/forum/viewtopic.php?f=1&t=15551#p62960согласно этому решению сделал следующее:
1. резервное копирование таблиц БД
2. jUpgrade обновил Joomla 1.5.23 jos_ префикс таблицы до Joomla 1.7 префикс таблицы j17_
3. установил PhocaGallery 3.0.2 (не обновление)
4. удалил все новые таблицы PhocaGallery 3.0.2 (j17_phocagallery *), за исключением j17_phocagallery_fb_users
5. выполнил SQL-запрос:
ALTER TABLE `jos_phocagallery` ADD COLUMN `metadata` TEXT NULL AFTER `metadesc`, ADD COLUMN `exttype` TINYINT(1) NOT NULL DEFAULT '0' AFTER `extid`, ADD COLUMN `language` CHAR(7) NOT NULL DEFAULT '*' AFTER `exth`;
ALTER TABLE `jos_phocagallery_categories` ADD COLUMN `extfbuid` int(11) NOT NULL default '0' AFTER `extauth`,
ADD COLUMN `extfbcatid` varchar(255) NOT NULL default '' AFTER `extfbuid`,
ADD COLUMN `metadata` TEXT NULL AFTER `metadesc`,
ADD COLUMN `language` CHAR(7) NOT NULL DEFAULT '*' AFTER `metadata`;
ALTER TABLE `jos_phocagallery_comments` ADD COLUMN `language` CHAR(7) NOT NULL DEFAULT '*' AFTER `params`;
ALTER TABLE `jos_phocagallery_img_comments` ADD COLUMN `language` CHAR(7) NOT NULL DEFAULT '*' AFTER `params`;
ALTER TABLE `jos_phocagallery_img_votes` ADD COLUMN `language` CHAR(7) NOT NULL DEFAULT '*' AFTER `params`;
ALTER TABLE `jos_phocagallery_img_votes_statistics` ADD COLUMN `language` CHAR(7) NOT NULL DEFAULT '*' AFTER `average`;
ALTER TABLE `jos_phocagallery_user` ADD COLUMN `language` CHAR(7) NOT NULL DEFAULT '*' AFTER `params`;
ALTER TABLE `jos_phocagallery_votes` ADD COLUMN `language` CHAR(7) NOT NULL DEFAULT '*' AFTER `params`;
ALTER TABLE `jos_phocagallery_votes_statistics` ADD COLUMN `language` CHAR(7) NOT NULL DEFAULT '*' AFTER `average`;
ALTER TABLE `jos_phocagallery` CHANGE COLUMN `language` `language` CHAR(7) NOT NULL DEFAULT '' AFTER `exth`;
ALTER TABLE `jos_phocagallery_categories` CHANGE COLUMN `language` `language` CHAR(7) NOT NULL DEFAULT '' AFTER `metadata`;
ALTER TABLE `jos_phocagallery_comments` CHANGE COLUMN `language` `language` CHAR(7) NOT NULL DEFAULT '' AFTER `params`;
ALTER TABLE `jos_phocagallery_img_comments` CHANGE COLUMN `language` `language` CHAR(7) NOT NULL DEFAULT '' AFTER `params`;
ALTER TABLE `jos_phocagallery_img_votes` CHANGE COLUMN `language` `language` CHAR(7) NOT NULL DEFAULT '' AFTER `params`;
ALTER TABLE `jos_phocagallery_img_votes_statistics` CHANGE COLUMN `language` `language` CHAR(7) NOT NULL DEFAULT '' AFTER `average`;
ALTER TABLE `jos_phocagallery_user` CHANGE COLUMN `language` `language` CHAR(7) NOT NULL DEFAULT '' AFTER `params`;
ALTER TABLE `jos_phocagallery_votes` CHANGE COLUMN `language` `language` CHAR(7) NOT NULL DEFAULT '' AFTER `params`;
ALTER TABLE `jos_phocagallery_votes_statistics` CHANGE COLUMN `language` `language` CHAR(7) NOT NULL DEFAULT '' AFTER `average`;
ALTER TABLE `jos_phocagallery` RENAME TO `j17_phocagallery`;
ALTER TABLE `jos_phocagallery_categories` RENAME TO `j17_phocagallery_categories`;
ALTER TABLE `jos_phocagallery_comments` RENAME TO `j17_phocagallery_comments` ;
ALTER TABLE `jos_phocagallery_img_comments` RENAME TO `j17_phocagallery_img_comments` ;
ALTER TABLE `jos_phocagallery_img_votes` RENAME TO `j17_phocagallery_img_votes`;
ALTER TABLE `jos_phocagallery_img_votes_statistics` RENAME TO `j17_phocagallery_img_votes_statistics`;
ALTER TABLE `jos_phocagallery_user` RENAME TO `j17_phocagallery_user`;
ALTER TABLE `jos_phocagallery_votes` RENAME TO `j17_phocagallery_votes`;
ALTER TABLE `jos_phocagallery_votes_statistics` RENAME TO `j17_phocagallery_votes_statistics`;
Все перенеслось и работает, видимых проблем нет.