After working intensely in a 300+ mg AD doc, certain AD functions no longer work. Quitting AD and bringing it up again solves the problem, and AD always remembers what I had just done (bravo!). I'm working with a MacPro with 24g of RAM with nothing else up except Mail. Does AD only access a limited amount of memory? Is the problem that its Undo remembers everything I've done in the session since I am manipulating many layers with hundreds of object? It may simply be a Mac memory problem. No big problem. Just wondering what the cause might be.