Here are the db changes that need to be performed for the upgrade.
ALTER TABLE #__comment_setting DROP set_sectionid,
CHANGE set_name note varchar(255) NOT NULL DEFAULT "",
CHANGE set_component component varchar(50) NOT NULL DEFAULT "";
ALTER TABLE #__comment
DROP usertype ,
ADD modified_by int(10) unsigned NOT NULL DEFAULT '0',
ADD modified datetime NOT NULL DEFAULT '0000-00-00 00:00:00',
ADD unsubscribe_hash VARCHAR( 255 ) NOT NULL ,
ADD moderate_hash VARCHAR( 255 ) NOT NULL,
ADD deleted tinyint(1) NOT NULL DEFAULT '0',
ADD spam tinyint(1) NOT NULL DEFAULT '0';
DROP TABLE IF EXISTS #__comment_installer;
DROP TABLE IF EXISTS #__comment_joomvertising;
CREATE TABLE IF NOT EXISTS #__comment_version (
`id` int(11) NOT NULL,
`version` varchar(55) NOT NULL
) DEFAULT CHARSET=utf8;
CREATE TABLE IF NOT EXISTS #__comment_queue (
`id` int(11) NOT NULL AUTO_INCREMENT,
`mailfrom` varchar(255) DEFAULT NULL,
`fromname` varchar(255) DEFAULT NULL,
`recipient` varchar(255) NOT NULL,
`subject` text NOT NULL,
`body` text NOT NULL,
`created` datetime NOT NULL,
`type` varchar(10) NOT NULL DEFAULT "html",
`status` tinyint(1) NOT NULL DEFAULT "0",
PRIMARY KEY (`id`),
KEY `status` (`status`)
) DEFAULT CHARSET=utf8;
UPDATE #__comment SET component = 'com_content' WHERE component = '';
in the code above replace #__ with your table prefix. Once you do the changes, navigate to the component settings -> delete the previous configurations and create new one. Now the comment system should work properly.
As far as the error you receive is concerned. Read it again and think what needs to be done! "No ccomment configuration exists for com_k2" ? What does our documentation says over here:
compojoom.com/support/documentation/ccomment/ch03s02s02
A hint: you have forgotten to create a k2 config
Regards,
Daniel