Over the years, we have seen a number of IIS related issues that cause trouble for users who deploy SQL Server 2005 Reporting Services. We have tried to resolve these in the MSDN Forums on a case by case basis. Now we have compiled the common issues with IIS into a single KB Article along with explanation of why these occur and what can be done to resolve them. Kudos to James Wu on the SSRS team for slogging through the issues and compiling them into this document.
How to troubleshoot IIS configuration issues in SQL Server 2005 Reporting Services
Take care and good luck,