This is NOT a big deal; a bit annoying if anything. When I exit CA4 by using CMD-Q or through the main menu, I get a crash message about a minute or two after the application was closed. It seems to happen after you have had the project opened for a little while, made a few changes, saved it and then quit. I am not sure if it's a matter of how long the project remained open or how many saves you made. Just now I tried: opened a project, made a few changes, then saved after about 10 minutes, and quit. And it happened again.

Attached is a screenshot of the message.

Note: again, it is not a showstopper because it doesn't affect the project itself but I thought I'd let you know, in case you begin to hear it from other users. It has been happening since day one; I think it was happening with CTA3 as well but I can't remember.