Wow, I can swear it used to work!
Same here. I can also swear it used to work. I know I've seen that situation, where those System ID files were missing, and the result was that Logic prompted for a serial on launch, and then everything was fine. Except that now I don't remember when or where I saw that, or even if it was my machine or someone else's. But I know I saw it.
I have a hunch that it indeed works that way, at least under certain circumstances. And isn't Guitarfreak's situation proof that it works that way? He's not telling us that Logic won't start at all. He's telling us that Logic prompts him to enter a serial, upon launch, and then he is able to work, until the next launch (or the next restart). Or at least that's how I understood him.
Hey Guitarfreak, have you tried Repair Permissions (as suggested above)? Here's a theory. When you tell Logic the serial, Logic tries to write the ProAppsSystemID file. But it can't do so because of a permissions problem. So then it prompts you for the serial again, on the next launch.
So I think you should try Repair Permissions. You could also check the permissions on your ProApps folder, by doing Get Info. On my machine, it says "Read & Write" for system and admin, and "Read only" for "everyone."
And David, here's an instance
of someone else noticing that it works the way you and I both said:
in Logic Pro 9, it puts the licensing info in the ProAppsSystemID and not the Logic Studio System ID. You can demonstrate this by removing the Logic system id and starting Logic. It will not ask you to reauthorize. If you remove the ProAppsSystemID and restart, it will ask you to reauthorize.
By "reauthorize," I think he doesn't mean 'reinstall Logic.' I think he means enter the serial into a dialog presented by Logic, as part of the Logic launch.
And someone confirming this behavior regarding Final Cut is here
(and he shows a picture of the dialog, and I know I've seen that dialog before). I realize Final Cut and Logic might not use the same authorization scheme, but it would surprise me if they didn't.
OK, here's the clincher. This behavior is also confirmed by Apple
If Final Cut Studio (2009) or Logic Studio (2009) are also installed on the system that you remove the ProAppsSystemID from, you will have to re-serialize those applications when opening them.
Apple doesn't say 'you will have to reinstall those applications in order to re-serialize them.'
So this is all pretty mysterious, and I don't know why you saw a different result in the test you just did.