WP - Not sure if it's the (external?) reader or the computer. You're saying that you have an external reader connecting to your Macbook, and when you use a cheap CF card it reads fine but with the a high performance CF card it doesn't read? If you are using an external reader, I can't see it being the Mac's fault: it has to be the reader (???), as the Mac doesn't care what the reader does: it should receive the data in a standard format independent of how the reader reads the card.

In theory, anyway.

Very very strange that connect your camera to your Mac (via USB I would guess) and that it cannot see the camera as a separate HD if you use the Pro card, but does see it if you use a non-Pro CF card. I wonder if the Pro card is bad?