Try checking in sql server 2008 configuration manager for the port assigned to your instance under network configuration -> TCPIP -> Properties. Cut the TCP dynamic port and paste into the TCP static port. Then make sure you create a rule in your windows and hardware fire walls to allow pass through.
You'll also need to create a login in SQL server management studio with dbo access to the database and assign that user and password to the data source in report manager.
This worked, and I got it through our Gold Partner incident support straight from a high level Microsoft tech, not the half complete solutions I've seen here.
Honestly, sometimes I think these forums are like old lady bakers. They give you part of the recipe, but leave out the secret ingredient.
You should also check the doc file for typos. It references both C: and D: drives for the dlls and reporting services.