[dnanian]

Ah, that's probably because you didn't mount the sparse image (using Disk Utility) before trying to restore from its volume.

DMGs can be restored "directly", but Sparse Images need to be mounted first...

Very strange/interesting error from Disk Utility... ooof.

If you want to run SuperDuper! from a case sensitive volume, create a small sparse image that isn't case sensitive and copy SD! to it. Then, mount that image and run SD! from there...