the new cron in 4.2 activates the pam access module. if you have been using that to control ssh access or other things, now suddently cron is going to use it as well. this only seems to affect user crontabs and crontabs in /etc/cron.d. from some digging around i was able to determine that cron sets the tty to 'cron', so you can just add a line like: +:ALL:cron
to /etc/security/access.conf and it will enable those cron jobs again.
NOTE: this is only if you already have modified access.conf. if you haven't touched it, then you don't need to do anything. i just happened to notice: Oct 21 11:15:02 charon pam_access[27438]: access denied for user `root' from `cron' Oct 21 11:15:02 charon pam_access[27439]: access denied for user `cacti' from `cron' Oct 21 11:15:02 charon crond[27438]: Permission denied Oct 21 11:15:02 charon crond(pam_unix)[27438]: session closed for user root Oct 21 11:15:02 charon crond[27439]: Permission denied Oct 21 11:15:02 charon crond(pam_unix)[27439]: session closed for user cacti
in some logs while i was looking for other things...