polipo's cron script use sudo to become user polipo. I think it will be better to use su. So polipo will not depend of sudo.
Created attachment 90687 [details, diff] polipo_crond.patch
fixed in cvs, without revision bump. I guess you altered the default shell of the polipo user. I had to force -s /bin/sh for making it work with the default shell is /bin/false.