Thanks to R.K. McSwain for pointing out that at least one user has reported unexpected shutdowns from AutoCAD (Architecture, probably) following installation of the 2018.1 Update. The problem went away following uninstallation of the update.
Anybody else have any issues or are you all waiting for the early adopters to find out for you?
Edit: it turns out the crash occurs when opening 2013 DXF files.
Edit 2: a hotfix has been posted here.