You could face this issue while connecting to Reporting Services from configuration manager.
The below error mainly appears while accessing Web Service URL property in Reporting Services configuration manager and the main reason behind is a broken\invalid <UrlString> tag.
To confirm this go to location mentioned below and open rsreportserver.XML file in notepad. \Program Files\Microsoft SQL Server\MSRS10.SQL2008_PROD\Reporting Services\ReportServer
Resolution: Correct the <UrlString> </URLString> accordingly and save the file, and it should work now.