If you have an application that uses SQL Server Reporting Services and you are seeing errors similar to this:
ReportServerException: The report server has encountered a configuration error. Logon failed for the unattended execution account.
You may have an inappropriately configured “Execution Account” for Reporting Services. If you browse to your Reporting Services log at C:\Program Files\Microsoft SQL Server\MSRS10_50.MSSQLSERVER\Reporting Services\LogFiles (your specific location might be different) you will find an entry similar to this:
ERROR: Throwing Microsoft.ReportingServices.Diagnostics.Utilities.LogonFailedException: Logon attempt for user ‘username’ failed.
Okay, so by now you are probably wondering how to fix this. It’s quite simple actually. On your SQL Server, load up the Reporting Services Configuration Manager. Connect to the Reporting Service that is having the problem and then click on the Execution Account tab on the left. Specify a known working user account (local or domain) and click Apply. Your Reporting Services should now be working once again!