OK, I turned System Restore (SR) off, which zapped all the restore points, rebooted, created a restore point, then ran a scan. Same result; every file in the System VolumeInformation/_restore subfolder is password protected. Now that there’s only one restore point in it, most of the files are .png (portable network graphics) or .js (JavaScript) files.

That these files are suddenly not scanable is not a big deal, but it signals that something in my system or the Avast software changed 2 weeks ago, and that’s what bothers me.