Nick,
It may be the same problems several of us had with crashes on close. See this thread:
http://archicad-talk.graphisoft.com/viewtopic.php?t=5352.
I finally cured mine by clearing every ArchiCad, PM & Graphisoft preference and cache file, then resetting permissions. This meant I had to reset all my keyboard shortcuts, desired pallette shapes, etc.
I suspect that it was related to a Mac security update, though I don't know for sure.
My grandparents lived in Den Haag, until a wayward American bomb landed on their house in 1944, and they moved to Laaren.