I'm running Webmin 1.5 on Fedora 12 with both cron and anacron installed. Cron jobs in the /etc/cron.daily, /etc/cron.weekly, and /etc/cron.monthly directories are not being displayed/managed in Webmin.
Fedora moved invocations of the daily/weekly/monthly 'run-parts' command to the /etc/anacrontab file while previous versions put the run-parts calls in /etc/crontab. It looks like Webmin doesn't recognize that /etc/anacrontab file, so none of the daily/weekly/monthly jobs are being detected.
Webmin does recognize the files in /etc/cron.hourly. Those files are called through /etc/cron.d/0anacron which executes 'run-parts /etc/cron.hourly'.