We've found that [Microsoft Update KB4041681] is causing problems. In it, Microsoft notes:
Installing this update may cause applications based on the Microsoft JET Database Engine (Microsoft Access 2007 and older or non-Microsoft applications) to fail when creating or opening Microsoft Excel .xls files. The error message is, ''Unexpected error from external database driver (1). (Microsoft JET Database Engine)''.
If you can roll back to a restore point prior to this update or uninstall the update, it should work again.
Microsoft states in the article that they are working on a fix for these issues.