[dnanian]

No, I don't think you're doing anything wrong: it looks like Spotlight is working hard on the drive that's being backed up, and for some reason that's causing the index to not be copyable.

v2.0 handles this differently, but for now wait until Spotlight has stopped indexing your drive (the magnifying glass has a dot in its middle that should stop flashing), and then do your backup. At that point, it should work OK.

You should also take a look at the FAQ: I've written an entry that explains how to use SuperDuper! to disable indexing on the backup drive, which might prove useful to you as well.