I have several problems with several Windows computer on one network using DHCP to give out addresses. When you boot up the computer the get there addresses, gateway, and dns numbers fine, but in about an hour the dns numbers change to the old dns numbers they used, which are no longer valid. you can do a renew on the network card and everything is fine for about another hour. I have run all the updates on the pcs. I have even tried to move the dhcp server from the windows server to the router, but it never seems to help.