[PLUG] question on trying to fix local lan connection

[website reader]

I have always upgraded my Ubuntu files using the automatic Upgrade
Manager.  Unfortunately, I have lost the ability to talk from my main
computer to 2 other machines on the LAN network.  What do I need to
do, so that I can talk to them?  The dhcp3 server seems okay, when
enabled by the "service isc-dhcp-ipv4 restart" command, but running
tcpdump at the client computers shows that no IVP4 information is
being exchanged but strange bootps IVP6 information is occurring.

How do I fix all this, so I can talk from the sever to the 2 clients?

(p.s.: I hate doing Ubuntu upgrades and losing local connectivity)