When I imported the XML and did updates in the problem diagram I got this error instead of it crashing:
DAO.Field [0x00000c5b] The field is too small to accept the amount of data you attempted to add. Try inserting or pasting less data.
My update could be as small as moving a connector position. The error happened when saving the the diagram, but it did not crash EA any more. That way I was able to detect which element caused the crashing, but not why!!