IIS reserves port 80. SQL 2008 reporting services is now using it’s own ‘web server’ – HTTP.sys.  In reporting services configuration manager change the Report Manager URL advanced settings.  In the ‘Multiple Identities for Report Manager’, edit the entry and change the TCP Port to not be 80.  Common alternates are 8080 or 8000.
http://technet.microsoft.com/en-us/library/bb630449.aspx