How are you entering the serial numbers? Are you signed in as administrator or are doing this from a regurlar user account? Try to enter the serial number as an administrator.
One problem with the serial number may be, that you migrated an old "ProAppSystemID" file, that may be corrupted or write protected.
- 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.
All this has to be done with administrator privileges, because the ProAppSystem ID needs to be stored in the system library.
Sometimes Aperture writes this file 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
your MacintoshHD/Library/Application Support/ProApps/ProAppsSystemID
You do not need the original install disks to reinstall Aperture.
You can download the Aperture Trial here:
Delete your current Aperture version from the Applications folder, then run the Trial installer and immediately update using "Software Update" from the -menu.
Then launch Aperture and enter your serial numbers, all while signed in as an administrator.
You will have to enter both serial numbers - the original version 2 number and the upgrade serial.
Otherwise there is no difference between the Trial version and the version sold on the installation media.
BTW, since you are using Mt. Lion - since MacOS X 10.7 and later the "Automatic Termination" in the process system may keep the processes stored in the RAM, without really quitting the program, even if you use the "Quit" command. If you see no effect, after removing preferences or other files from the libraries, repeat the process, but log off and on again after moving the files. Otherwise these files may be restored from the caches.