a bad public movie atom error????

It's a corrupt file -- QT stores information in what it calls "Atoms" and a bad one is one that's been corrupted.

Happens alot with Zipped files -- shouldn't happen at all unless the file itself is packed in some manner. Best bet is to create the file again, or get it again unzipped from wherever you got it in the first place. There is no way to repair it (although some programs, like VLC, can apparently open it without error -- that won't do you any good insofar as the iPhone and iTunes is concerned).

This is happening, in my case with files that have not been packed in any manner. The files work on my desktop at home (XP). I transfer them to my iPod (w/ Disk Use Enabled) then to my laptop (Vista). Every one of them produces the same error when I try to play them on the laptop.

Furthermore, when I transfer them back from the iPod to the desktop, they play fine on the desktop.

It can happen with any files -- it's just that compressing them makes it more likely.

And they can continue to play just fine otherwise -- but give errors when transferred. Just redo them and you should be fine (although if it happens with all your files I'd stop using what you are using to make them and use another product).

But if I copy the file from desktop to laptop, it does not work on the laptop, then transfer the non-working file back to the desktop from the laptop and it works on the desktop, that should indicate it is not actually a problem with the file, no?

No, it could still be an issue with the file.

The file is probably corrupt but your program on the desktop doesn't mind that (and yes, even if it's the same version of iTunes -- there are just way too many variables on a PC that can affect things, like QT versions, display cards, etc. etc).

The file(s) is bad -- the fact that is plays okay one place doesn't mitigate this. Either you fix the file so it plays everywhere, or you don't worry about playing it on your laptop.