Comment 3 for bug 317128

The problem obviously come from line 47 in the postinst script:

 update-rc.d ntp multiuser 23 >/dev/null

The multiuser keyword seems unknown to update-rc.d

Replacing multiuser with "defaults" - I did it manually now by editing /var/lib/dpkg/info/ntp.postinst - lets me install the package properly, or, in this case now, fix the broken install with
apt-get install -f