No sweat.
My latest guess points me to the file having a bad extension. It has happened to me once or twice before: a .wmv file wouldn't play because it actually wasn't .wmv. I tried a couple of extensions (I don't even clearly know why I did this) and BAM! The file played a-ok.
Anywho, try VLC or Mplayer (
www.videolan.org/vlc/ and
http://www.mplayerhq.hu/homepage/design7/news.html respectively). Each should be capable to play the file.
I also figure that the file might have chapters in it, and that's why it's not playable by iTunes. The fact that LW player plays it straght through is because (if I'm right about the chapters thing) that player doesn't have a Chapter select feature (that I know of
)