I do a nightly SuperDuper! clone on my MacBook Pro. Ever since updating to their latest (Lion-compatible) version, it won't do a full clone, but the logs report copy failures because of Input/Output errors. (Unfortuantely, the previous version successfully completed clones, but did not report the errors and simply did not copy the files).
Sure enough, if I try to copy the files it reports, in the Finder or via command line, it also fails. Every time I delete one of these offending files, and try to run a new clone, it finds another file that can't be copied (this has happened three times so far).
Obviously I'm thinking this hard drive is ready to crash, but is there a way to verify? Disk Utility reports no problems.