Yes, I've done it and Disk Utility doesn't think there's anything wrong. But yet, I've tried over and over to make a disk image - of different disks, even - an

Yes, I've done it and Disk Utility doesn't think there's anything wrong. But yet, I've tried over and over to make a disk image - of different disks, even - and every single time I get the error "no usable disk image found". At this point, after having scoured the web for clues, I can only conclude: this is a bug in MacOS. I'm now trying to do a full update to the latest release, and see if it works beyond that point - but if it doesn't, the good ol' tarball approach is all I've got left. I think Apple has some QA issues.