There are two URL's setup under Report servers for SSRS, i.e. Report Manager URL and Web service URL. These must have the following format.
http://SERVERNAME/ReportServer
If there are too many forward slashes, or not enough, or you have tried to use a UNC path, etc., then you will get the error "Invalid URI: The Authority/Host could not be parsed".
Exactly what URL's did you use that generated the error?