I too have had the problem with can't-move-to-library errors
on downloading. it seems to happen with "bad" file names
(containing special characters used by the O/S, like slash or colon)

--but I don't have a solution. is there some way to rename a
file in transit? this is very frustrating, as it always happens with
something I *really* want and never see! :-P

I guess this is a "new feature request", along with a plea
to help us out with at least a list of messages/notations and
what they mean so we can stop beating our heads looking for
what's wrong. (oh dear. yes. documentation.)