renamed PreviouslyAcquired.db to PreviouslyAcquired.db.old, then reconnected the camera and went through the wizard again, where I was able to import the pictures a second time.
As noted in the comments below, in order to see the PreviouslyAcquired.db file, you first need to turn on Show hidden files, folders, and drives in Windows’ Folder Options dialog box. To do this, open Windows Explorer, click on Organize and choose Folder and search options to open the Folder Options dialog box. Choose the View tab, then choose the Show hidden files, folders, and drives radio button under Hidden files and folders.