Access is denied. Check that the Default Content Access Account has access to this content, or add a crawl rule to crawl this content.
So you have the following error: "Access is denied. Check that the Default Content Access Account has access to this content, or add a crawl rule to crawl this content" in your Event Log and you have no clue why your Search Content Service Account can't access the data for indexing, although it has all the right permissions and you double checked that it does.
Well then your SharePoint 2007 server instance is most likely running on a Windows Server 2003 SP1 and you're using different of host headers for different web applications. You see Windows Server 2003 SP1 includes a loopback check security feature that is designed to help prevent reflection attacks on your server and authentication fails if the FQDN or the custom host header that you use does not match the local computer name.
Want to fix it? Go to: http://support.microsoft.com/default.aspx/kb/896861