For some reason, I can't play some .avi files in Quicktime. I'm using Leopard and I have 'Perian' installed. Most of my .avi movies play, but I just downloaded a batch of 10 files and when I try to open them I get the error message: "The movie could not be opened. The file is not a movie file. I know the files themselves are fine because they worked on an old PC. For some reason, I just can't get them to work in OS X. Also, I would prefer to use QT over VLC... any advice would be greatly appreciated. Thanks!!