This section describes the Web Part installation steps if you have configured a medium or large Network Load Balancing Server Farm environment, as described in the Microsoft article in the resource kit:

http://www.microsoft.com/technet/prodtechnol/sppt/reskit/c1261881x.mspx

For the Archive Search Web Part to be installed correctly, SharePoint virtual servers and Web applications must be configured to use host headers and not IP addresses.