I exported a loft into a route, and noticed that it was already present via another name. So I renamed it, and reexported and ran into this error.
May be a software issue, but the game instantly quit, and it wasn't really what I needed. Anyone else had this problem before? It looks to be Visual C related, but I have never seen it before, and I think I updated VC recently, but who knows.
Very unwelcome interruption to the progress.