help with cron/rsync error message

[steve%prd.co.uk@localhost (Steve Blinkhorn)]

I have two servers next to each other in a data centre.  I use cron
jobs to back up data each way betwen the two, using rsync.  In the
course of this year I have upgraded both to amd64/9.2, but leaving all
the cron/rsyncd.conf etc. config in place.  I checked that everything
ran normally back in July, but now I find /var/log/cron is full of
lines like this:

Nov 14 22:02:00 trafalgar cron[3913]: (CRON) pam_authenticate failed
(System error) 

hosts allow is set in a [global] module to include the address range
that encompasses both machines in both machines'.rsyncd.conf files.

Where to start?

-- 
Steve Blinkhorn <steve%prd.co.uk@localhost>