I look up the webservices using the domain name of the server
Your statement above states "domain name." Whether this is to the Internet or an Intranet, this does not make a difference.
If you have a DNS server implemented in your Intranet, then changing the IP address should not effect anything, if you indeed look up the services with the domain name.
If you do not have a DNS server implemented in your Intranet, then your statement above does not make any sense.
[ November 12, 2008: Message edited by: James Clark ]