> What is the difference between a MAC-created and a
> Windows-created file with the same MIDI data?

None. That's the point of an interchange format.  My guess is
Cakewalk puts in a (perfectly standard) message that csound 
can't process, but as usual, i don't know anything.  If you'd
save a small midi format 0 file (< 10 events, please!) for me, 
though, I can have a look at it.