Aperture 3 accepts my serial number, but won't save it between launches

Thanks for the suggestions, Frank. I tried removing the preferences file, as well as the ProAppsSystemID file in /Library/Application Support/ProApps, but neither one helped. The logic board was replaced at the local Apple Store, but I'm not sure the Geniuses there have quite the expertise for this kind of thing, so I'll probably just call AppleCare. I thought I'd start by posting here, just in case someone would have a quick answer that would save me the trouble of calling Apple. I'll definitely post another reply when I have an answer.

Okay, one important clarification from my last post. I said that I tried removing the file: /Library/Application Support/ProApps/ProAppsSystemID, but that's not quite right. From the same directory, I removed a file called "Aperture System ID" and that was not helpful, but apparently I had not tried removing the ProAppsSystemID file. I noticed that right after my last post, and when I removed the ProAppsSystemID file and relaunched Aperture, it came right up and worked perfectly. I checked the About... box, and all the correct information was displayed there. So, the problem was the ProAppsSystemID file, and the solution was to throw it out. I'm not sure what that file is for, or how it got there, but apparently Aperture is perfectly happy to run without it, so I'm happy too.

Actually, I was curious about that myself, so I already looked. The file did NOT get recreated! I was surprised, because now I have to wonder what the file was for, and how it got there in the first place.