Ошибка при установки Joomla

" Specified key was too long; max key length is 767 bytes SQL=CREATE TABLE `uxyn8_session` ( `session_id` varchar(200) NOT NULL default '', `client_id` tinyint(3) unsigned NOT NULL default '0', `guest` tinyint(4) unsigned default '1', `time` varchar(14) default '', `data` mediumtext default NULL, `userid` int(11) default '0', `username` varchar(150) default '', `usertype` varchar(50) default '', PRIMARY KEY (`session_id`), KEY `whosonline` (`guest`,`usertype`), KEY `userid` (`userid`), KEY `time` (`time`) ) DEFAULT CHARSET=utf8"

Что делать