If you install Aperture 2 into a new Snow Leopard machine for a non-admin user you get this error message "The license file will not be written to disk because the user does not have enough privileges".
The workaround is to make the user an admin, then login and enter the serial number, then make them a non-admin.
Very annoying, esp. since 10.6 admin privilege changes require a restart! (In prior versions of OS X a restart was not required.)--
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