Cron jobs stuck in drupal 6 I am maintaining a site on drupal 6. I have installed a birthday module which can send mails to users on their bday. But it doesnt do so. None of the other cron related tasks are done, though cron runs daily, and I do get a notification on mail . I tried to install a new module called ultimate cron (6.x-1.7), this could solve my problem earlier when I last installed it. But on re-installation this also doesnt work. None of the triggered rules that should be fired on cron run are fired.

On site config -> cron it lists all the processes, but they are in starting state. And on background process page , it shows first task with 0 progress n none other are being processed.
I have tried to install latest version of ultimate cron modules, but that gives some error saying "Unknown field: start stamp".
Please help me with this.
For the latest version of Ultimate Cron, you also need the latest versions of Background Process and Progress. The versions might not match, or the database schema may not have been updated properly. Try completely uninstalling Ultimate Cron, Background Process and Progress, and then re-install them.