SCOM 2007 R2: report server cannot decrypt the symmetric key that is used to access sensitive or encrypted data in a report server database
Currently I was deploying SCOM 2007 R2 reporting server component, the OS of the computer is Windows 2008 R2 and I used SQL 2008 SP1 reporting component on it. (follow this article to install SQL 2008 SP1 on Windows 2008 R2 à https://support.microsoft.com/kb/955392)
The SCOM RS installation did not complete successfully and I have the following error in the event viewer: report server cannot decrypt the symmetric key that is used to access sensitive or encrypted data in a report server database
The solution to this is to uninstall the SQL reporting service and installing it again and choose to run the reporting service under the SCOM DB Reader Account, then install SCOM 2007 R2 reporting component and it will work fine with you.