[root@rh43repo-cab4 rhn]# up2date -d --installall --channel=rhel-i386-es-4
No such allowed channel:  --channel=rhel-i386-es-4
[root@rh43repo-cab4 rhn]# up2date --show-channels
rhel-i386-es-4
rhel-i386-es-4-extras
rhel-4-es-i386-rhaps-2

Try this up2date -d --installall=rhel-i386-es-4