Retransferring clone back to blank drive doesn't copy all files

I've upgraded my internal HD to a bigger drive. In order to preserve my data, I've cloned the full volume to an external drive, inserted the new (blank) internal one, booted from the external one and copied back my data with "erase, then copy". SuperDuper finished with no errors.

According to the the progress window, only 755.882 of 769.838 have been copied back to the new drive. What happend to the rest? Were all the remaining files corrupted? Did some safeguard/copy protection prevent those files from being copied? Why would SuperDuper refuse to restore 2% of my backup?

EDIT: Some more information:
- Backup is of the full volume, not just the home folder or a sandbox
- The new volume is larger than the old one, it's not a space issue
- I did a SMART and surface scan on the new internal drive, no errors
- I'm on 10.6.1 using SuperDuper 2.6.2 (v87)