Thank you for responding. I use a PC and I only have 4 Gigs of RAM, and I know I should have at least 8 to fully utilize Premiere Pro, but it is what it is. I also use Microsoft Security Essentials. But, what I didn't understand is that it only happens when I access AE. I've got lots of videos on Premiere CS6, and I never, ever get that warning about the disk being full when I access it.
Oh well. When it becomes a real problem I'll make sure I get to the bottom of it. For now, it's not keeping me from doing anything, but it's quite annoying.