I just got a new Western Digital 250 GB external Hard Drive (with firewire) to store my videos and music. When I copy my video (in avi. format) to and from the drive, I get blocks of color all over the picure during playback. This doesn't happen to mpeg files. I'm thinking it's a size issue since the avi's are so much larger, but that shouldn't be an issue unless I'm mistaken. Any ideas?