Mental note #1: if using host headers with MOSS (or IIS) ensure the web server is configured with a static IP address or the NIC’s MAC address is reserved within DHCP.
Mental note #2: Just because it’s SharePoint, don’t forget the easy things! No, really!!!
I came across an unusual problem today after a MOSS server was imaged and restored to a new physical blade: Central Admin, the default SSP web app, and a specially-created sanity check web app were all working beautifully but the single site configured with a host header refused to load.
In addition, the Application event log was full of errors suggesting a database server connectivity issue:
The start address http://site.com cannot be crawled. The item could not be crawled because the crawler could not connect to the repository.
The database connection wasn’t the problem but nevertheless, SharePoint couldn’t find what it was looking for. The WFE’s NIC changed as part of the migration, which meant a new MAC address, and therefore a new DHCP lease for a different IP address that DNS knew nothing about.