Aperture 3 asks for my SN (after update) and won't accept my Ap2 to 3 'Update' SN

I have just downloaded an update to Aperture 3 following a system 'update box' notification.

Now, when trying to open Aperture it asks for the SN. When I enter the Aperture 3 SN from the software box it rejects it saying that was an 'update' SN, and it needs the original SN (which I have for Aperture 2).

I am on my MacBook Pro, running Lion (OS X 10.7.4)

I have seen a couple of the other similar questions, but they seem to refer to Mountain Lion...

Any ideas please?