I just upgraded from 4.1 to 5.5 and I can no longer get DHCP leases. I have found that if I /etc/rc.d/init.d/ipchains stop then I can renew leases. Shouldn't the server be configured to allow DHCP requests if I setup the configuration to serve DHCP on the local network? Also, I looked for the ipchains configuration file at /etc/sysconfig/ipchains (as seems to be expected in /etc/rc.d/init.d/ipchains) but it does not seem to exist.