Apple has just published a new
KB article to address a couple of problems, "After you upgrade Aperture from an earlier version to Aperture 3, Aperture may quit unexpectedly when opening or when you enter the Aperture 3 upgrade serial number." (However nothing yet, unfortunately, on the widely discussed memory leak problem.)
On the same page are links to related topics:
* How to properly reinstall Aperture....;
* How can I change a serial number;
* Is Aperture licence good on multiple machines;
* More questions about Aperture Library backup.
__________________
Gazza
AKA FarmerGaz on twitter.com/FarmerGaz

Doubt is the beginning, not the end, of wisdom