I don't think it's a sound problem, Burr. The way I read it, it's more to do with associations in that a file won't play when he double clicks, but does if he drags and drops.
Your suggestion regarding playlists could solve the problem though.
Either way, Elliok, come back and let us know. That way we can keep trying if it hasn't worked, or if it has we'll know what to suggest if anyone else has the same problem in the future. There is intelligent life on Earth, but I'm only visiting.