This means that the installation script couldn't add back the categories. It's probably because it couldn't create the table.
Go in your database, then in the SQL menu and copy/paste that query and run it:
CREATE TABLE IF NOT EXISTS `jos_hikashop_category` (
`category_id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`category_parent_id` int(10) unsigned NOT NULL DEFAULT '0',
`category_type` varchar(255) NOT NULL,
`category_name` varchar(255) NOT NULL,
`category_description` text NOT NULL,
`category_published` tinyint(4) NOT NULL DEFAULT '0',
`category_ordering` int(10) unsigned NOT NULL DEFAULT '0',
`category_left` int(10) unsigned NOT NULL DEFAULT '0',
`category_right` int(10) unsigned NOT NULL DEFAULT '0',
`category_depth` int(10) unsigned NOT NULL DEFAULT '0',
`category_namekey` varchar(255) NOT NULL,
`category_created` int(10) unsigned NOT NULL DEFAULT '0',
`category_modified` int(10) unsigned NOT NULL DEFAULT '0',
`category_access` varchar(255) NOT NULL DEFAULT 'all',
`category_menu` int(10) unsigned DEFAULT '0',
`category_keywords` varchar(255) NOT NULL,
`category_meta_description` varchar(155) NOT NULL DEFAULT '',
`category_layout` varchar(255) NOT NULL DEFAULT '',
PRIMARY KEY (`category_id`),
UNIQUE KEY `category_namekey` (`category_namekey`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 ;
Then, install again HikaShop and hopefully you should get back your categories.