cron permissions problem

[Adam Kessel <adam@bostoncoop.net>]

I've recently installed Woody on a couple of systems (one new-ish laptop,
another dinosaur desktop) and upgraded a few things to testing/unstable, and
noticed that cron doesn't work. In auth.log I see: 

Aug 29 17:10:01 joehill cron(pam_unix)[3550]: session opened for user news by (uid=0)
Aug 29 17:10:01 joehill CRON[3550]: Permission denied
Aug 29 17:23:01 joehill cron(pam_unix)[3567]: session opened for user mail by (uid=0)
Aug 29 17:23:01 joehill CRON[3567]: Permission denied
etc..

No individual cron jobs work either (i.e., set up with crontab -e).

I've checked the permissions on all the files in the cron package and they
are identical to the permissions on a working system. I've also eliminated
cron.allow and cron.deny, and also created cron.allow with the relevant user
names in it. I've reinstalled cron with apt-get.  I also have installed at
and anacron, but I don't think they make any difference to cron.

I've looked through everything in /var/log for clues, but nothing stands
out.

I've also searched the web for this problem and was only able to find one
posting by someone with a similar problem, but there were no responses.

I'm using cron v3.0pl1-72.

Can anyone suggest how I might go about troubleshooting this? I'm rather
stuck for options to explore.

Thanks for any advice--
---
Adam Kessel (adam@bostoncoop.net)