Can you delete the table again and try to recreate it using the following command:
CREATE TABLE IF NOT EXISTS `piwik_report` ( `idreport` int(11) NOT NULL AUTO_INCREMENT, `idsite` int(11) NOT NULL, `login` varchar(100) NOT NULL, `description` varchar(255) NOT NULL, `period` varchar(10) NOT NULL, `hour` tinyint(4) NOT NULL DEFAULT '0', `type` varchar(10) NOT NULL, `format` varchar(10) NOT NULL, `reports` text NOT NULL, `parameters` text, `ts_created` timestamp NULL DEFAULT NULL, `ts_last_sent` timestamp NULL DEFAULT NULL, `deleted` tinyint(4) NOT NULL DEFAULT '0', PRIMARY KEY (`idreport`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8;