I tried burning the original file plus a 7M version of the file to a blank disk and neither one was readable (either by WiiMC or mplayer CE).
I also tried several more files on the original disk and found that eventually WiiMC could read the later files.
This is strange behavior and looks like it’s just a disk reading poblem, except that mplayer CEcould read the original file. Is it possible that mplayer CE just does less seeking or something, in a way which reduces the chance of errors?