crontab returned non zero value: chown: Operation not permitted
it's most likely related to the +s flag on the crontab binary.root@server:~# ls -la /usr/bin/crontab
-rwxr-sr-x 1 root crontab 34760 Jul 3 2012 /usr/bin/crontab
root@server:~# chmod 4755 /usr/bin/crontab
root@server:~# ls -la /usr/bin/crontab
-rwsr-xr-x 1 root crontab 34760 Jul 3 2012 /usr/bin/crontab