It looks like the R2 documentation is either wrong, or simply doesn’t apply when you’re trying to change the account for reporting services Sql 2008. I also found the online docs for 2008 didn’t match what I was seeing (detailed here:http://technet.microsoft.com/en-us/library/bb326213(SQL.100).aspx).

After changing the account in the configuration manager, the give away message was in the rsreportserver log:
“SharePoint content service is null. Report Server may not have joined the SharePoint farm.”

The following did the trick:

- Change the service account using the configuration manager.
- From SharePoint
–> Central Administration
–> General Application settings (not Application Management)
–> reporting services section
–> ‘Add a report server to the integration’ – enter your admin credentials to allow grant RS access.

Cheers, Ryan

Original post by Ryan Simpson on 17th November 2010 here: http://rionisimpsoni.wordpress.com/2010/11/17/changing-the-user-account-for-reporting-services-2008-not-r2-in-sharepoint-2010-in-integrated-mode/