Kees,
Be sure to enter the serial number, when you are logged in from an account with Administrator priveleges - otherwise can it not be stored.
Aperture is installed for all users on your mac, so the serial number is written to the system library, not the user library, and this requires read/write access for administrators. Do you enter your serial number using an administrator account?
I did problem still occures.
Does the mini not accept the serial number (error Wrong serial number) or is it asking over and over again on start-up?
If the mini does not accept the serial number, check if you confused some letters, when you wrote the serial number down and enter it again, see: Troubleshooting Professional Application Serial Numbers
If it is accepting the serial number, but forgetting it, you still may have an older ProAppSystemID file or Aperture cannot write to the System Library.
To stop Aperture asking for the serial number, first check, if you still have an old file "ProAppSystemID" in your System Library.
- Quit Aperture.
- Go to your MacintoshHD and open the folder "Library", then "Application Support", then "ProApps".
- Remove the File "ProAppsSystemID" to the Desktop, if it exist and restart Aperture.
- Reenter your serial number, hopefully for the last time.
Sometimes Aperture writes this file "ProAppSystemID" to a temporary directory, when it cannot write to the Library. If the above does not work, look at the temporary directory /tmp
Use the Finder's "Go" menu
Go > Got to folder and enter /tmp into the textfield. If you see the file there, move it to its proper location.
Léonie