My advice is also look at cron_schedulecron_schedule
table if you debug cron. If you did it you could understand that the problem is following:
exception 'Mage_Core_Exception' with message 'Invalid model/method definition, expecting "model/class::method".' in /var/www/local.dev/www/mg18com/app/Mage.php:595
exception 'Mage_Core_Exception' with message 'Invalid model/method definition, expecting "model/class::method".' in /var/www/local.dev/www/mg18com/app/Mage.php:595