User Crontab is outside of GUI session
When trying to execute programs that require variables from the GUI session. the crontab fails. It can no longer execute tasks which relate to editing gnome gconf or any other session settings.
I believe this is because the crontab is outside of the gnome session. There are two possible fixes, 1) Somehow allow the system cron to access session variables when users are logged in, 2) Create a special cron which runs when users log in.