So, Apple Aperture 3.0 is ridden with bugs. One of the most annoying ones is that it becomes stuck processing… when Faces are in the queue. Even 32-bit mode won’t save you until you process the non-faces items first. So, you’ll need to disable faces for the time being.
How to disable Aperture Faces:
Go to the Aperture>Preferences menu and under the General tab.
Turn off Enable Faces.