I suspect it's this machine, or something with 10.4.10 (OS X)
I'm probably going to go through regular support channels. I just thought I might get lucky and someone would reply with, "oh yeah, that doesn't work", or some other quick answer.
Btw, midi tracks loaded with a vsti also have the same problem at 'audio to'.
Very odd indeed. (The "odd' ones always find me!