I have been using Archicad 13 for some time now and what I find is that more often than not it freezes for no obvious reason. I could be in 3d or floor plans the Archicad window just freezes. The title bar on top displays ( Not Responding) and then I have to quit Archicad or force it to shut down and then restart it.
I am using Archicad 13, on Vista ultimate, 4 GB ram, 512 graphic card, Amd 64x 2 processor.