Just to confirm, here's the line from /var/log/dpkg.log:
2013-07-15 09:10:20 upgrade isc-dhcp-server:amd64 4.2.4-6ubuntu3 4.2.4-7ubuntu1
So 4.2.4-6ubuntu3 had installed successfully with no problems, but 4.2.4-7ubuntu1 rejects the -user and -group options.
Just to confirm, here's the line from /var/log/dpkg.log:
2013-07-15 09:10:20 upgrade isc-dhcp- server: amd64 4.2.4-6ubuntu3 4.2.4-7ubuntu1
So 4.2.4-6ubuntu3 had installed successfully with no problems, but 4.2.4-7ubuntu1 rejects the -user and -group options.