When you have a server farm with three servers or more (e.g. web/search server, job/index server and database server, The job component on a different server than the web component) you might experience some problems with the search functionality after installing Windows Server 2003 Service Pack 1.
In the RTM version of Windows Server 2003 it is sufficient to grant the Sharepoint Admin account Power User permissions on the job/index server. But as of Service Pack 1 for Windows Server 2003, the account must have Administrator permissions. When you have configured the account as Power Users, the search functionality will stop functioning after the installation of Service Pack 1. To solve this, add the account to the local Administrators group.
More information: Searching no longer works on Microsoft Office Sharepoint Portal Server 2003