Upgrade to 3.5. Aperture 2 was a problem even with 10.7 and 10.8. There is no reason to expect software that old will continue to work indefinitely.
You'll be doing yourself a favor by upgrading. The new version is a much better application.
I am now wondering if it would be simpler to revert to my previous OS since I was perfectly happy with the performance of Aperture 2.1.4 and am not particularly thrilled by other Maverick changes.
I did not want to discourage you from upgrading to Aperture 3.5. It is worth it.I just mentioned highly useful precautions, to ensure you are safe, in case something happened during your upgrade.
You cannot downgrade your system to Snowleopard by simply installing the older system on top of your newer system.
- You will have to check, if some applications already have been upgraded to mavericks-only applications and files and databases been upgraded to Mavericks.
- Then make a backup of current backup of your entire system, better two backups and check, if they are working.
- Wipe your system drive by booting into recovery and running disk utility.
- Insert your snow leopard installer and reinstall snowleopard.
- Connect your backup drive and when prompted to migrate data abd settings,restore your data from the backup.