Its interesting that someone posted this. I was trying to create a rendering with my boss standing over my shoulder observing when he decided that there was something wrong. I tried to explain to him that ArchiCAD just wont stop. When it renders its like a car rolling down hill - its got so much momentum going that you just have to wait for a while until it slows to a stop. I've tried to repeatedly press stop or escape and ArchiCAD spites me by crashing.
I look at as a good excuse for a coffee break.
So, in actually responding to the question - no, I have no idea how to make it stop on command (although sometimes it will).
RA 2012 x64, Piranesi 6 Pro, Sketchup 8, Windows 7 Pro x64, Intel Core i7, 10GB RAM, ATI Radeon Mobile 5870