Drupal is an excellent open-source CMS but at the same time a bit harder to get hold off when things get bad without fairly advanced Drupal knowledge, recently I upgraded this blog from Drupal 5 to Drupal 6 and after making the site live with upgrade the Drupal cron-job started failing as evident in the picture below (the cron is setupped to run every six hours but it failed to do so).
Strangely enough running cron manually showed a 404, Page Not Found error, having tried everything from fixing cron commands to playing with cron.php file-permissions finally I found the reason of failed cron-jobs by having look at 'Drupal Log' which was showing error 'Cron run exceeded the time limit and was aborted.'