This is how I reverted to version 3.1.3.
1. Locate older version in whatever backup device you have and use it to replace version 3.2 in Applications then close.
2. Holding down both the option and apple keys, open Aperture using the icon in the dock.
3. A window appears with 3 options: repair permissions/repair database/rebuild database.
4. Go through all three, one at a time in the order they appear in the window. I closed after each operation and reopened, holding down the two keys to get access to the window again.
5. When I finished all three, I opened Aperture the normal way and everything - all books, projects, slideshows - was back in place and working fine.
I had only about 2000 photos in my library; the entire process took about 15-20 minutes.
At first I thought my vault was OK as well, but discovered it wasn't. My vault, which is in a partition of an external HD was so damaged by all of this that Disk Utility couldn't repair it. So I erased the partition dedicated to the vault, added a new one with a new name, updated it from Aperture, and now it, too, seems fine.
I hope this helps you. Good luck.