We deployed to a new server this morning with SQL Server 2008 running on it. Our software was trying to programmatically access the Reporting services api (found at: http://localhost/ReportServer/ReportExecution2005.asmx) This would work but if we used http://publicurl.com/ReportServer/ReportExecution2005.asm x then this would fail. This is because IIS doesnt allow you to access a domain if it is pointing back at the box you are on and if you wanted to use integrated authentication. This stuff is called loopback checking
To resolve this you need to make some changes to regedit: Follow the instructions found here: kb896861
This will enable you to set up hostnames that loop back to the local machine and will be allowed by IIS.