If anyone is interested, I have a save game that crashes every time.
I've done a little work on it with the debugger, and it seems to be memory corruption - not sure of the source. I've run it under valgrind a bit, and found plenty of complaints, but nothing obviously the cause. There is one persistent complain about accessing bytes 9-12 of a ten byte buffer, which would do it, except that I'd expect most allocated buffers to round to next word boundary anyway.
Not terribly helpful that, I know...