On a customer’s production environment, we encountered the following when trying to apply SQL Server 2008 x64 SP1.

“SQL Server Setup has encountered the following error:

A failure was detected for a previous installation, patch, or repair
during configuration for features [SQL_PowerShell_Engine_CNS,]. In
order to apply this patch package (KB968369), you must resolve any
issues with the previous operation that failed. View the summary.txt
log to determine why the previous operation failed.

Error code 0x84B20001.”

Our Fix

Tried a couple of different approaches discussed on the forums, however, the only thing that worked in our situation, was to completely uninstall SQL Server 2008, reboot, then re-install it.  After completing the re-installation, we re-attached the databases and applied SP1 accordingly.