Book port users and lovers, really!
When you download podcasts with juice and a download fails for whatever
reason it puts a .partial extension such as laughing_larry.mp3.partial.
These files won't play and won't work with the transfer program. The other
problem is if they are variable bit rate files but I doubt that is the case.
If you run juice again on that podcast and the download completes, the
.partial extension is removed. If you can come up with a particular podcast
episode that won't work, clue us in.
The real question might be, why bother with the transfer program. Unless you
want to process the file like changing speed and so forth, just copy to the
card and listen.