If you don't have access to aminet why not just singleclick the source disk's icon and then use icons/copy? I'd try to copy dos disks like Workbench first. Originals are often copy-protected and can't be copied so easily, if at all.
Also, tell us if the problem is when reading from source disks or when verifying the destination. In that case I'd try if formatting works. If not, there's probably something wrong with your drive...