To follow up on my last post.....a similar issue occurs when performing an edition upgrade to Notification Services, same error codes are returned but this time against the NS component. Checking the registry / file versions also reflect the same situation as before. The solution as you can guess is very simiar to that used for SSIS, but this time the file we are replacing is

NSService.exe

This lives in the ..\Program Files\Microsoft SQL Server\90\NotificationServices\9.0.242\bin directory

When I get some time I'll check out the remaining components and see what the score is with them