I am on SQL Server 2008R2 and got the above error from my RSS script, which was odd. How could it throw an error about Reporting Services 2005?
To resolve this, add the endpoint -e Mgmt2010 into the rs syntax. Example is shown below.
Executes script file contents against the specified Report Server.
-u username User name used to log in to the server.
-p password Password used to log in to the server.
-e endpoint Web service endpoint to use with the script.