I have had mixed results with "retry" duplicates, some have worked, and some have given similar errors as in your post. With the daily hotfix and MP upgrades, it's hard to pin down legitimate bugs vs. user error on my part. I don't do manual duplicates on a regular basis.
In looking at your first post regarding performing a manual duplicate of an entire set- I think the key to this working would be if you are using unique 'Family Names' when you define your backup jobs. (this is found in the job properties under device & media) By default, Backup exec uses the Date & time the set is created, and this name remains valid as long as data can be appended, which can mean you have several days worth of backups in one family. My guess is that you want to manually duplicate one day's worth, not several days.
If you where define individual jobs with common Family names (like "Monday backup" or something) then your manual duplication could select "Monday backup" in the Restore resource list and all the servers you defined would get duplicated.
I think you'd really need to do some major tweaking to get Family Names, Media Sets, & Policies all working in synergy to get this right, but it seems possible.
-just my 2 cents