Thanks to Robert Green for pointing this out:
Microsoft is installing .NET 4.7 as part of their auto updates and it is causing many legacy Autodesk applications to crash on any ribbon interaction. Touch the ribbon, away goes your software.
If you can keep from installing the 4.7 framework do so. If the damage is already done then uninstall .NET 4.7 and install .NET 4.6.2 using this download link. Note that the uninstall of the offending version must be done first!
AutoCAD 2013 to 2016 and Inventor are affected, and possibly other products. BricsCAD users are unaffected.
It is also reported that you can work around the problem by hacking the registry to identify an earlier .NET version as being installed (the usual caveats apply). That’s described in this Autodesk Knowledgebase article that works around a related but slightly different issue.
Don’t you just love the way continuous automated updates enhance and enrich the user experience?