I have a Mac Pro and when I plug my Canon EOS Rebel Xti into the USB drive, it doesn't appear as a mounted drive. Instead what happens is the light for the CF card on the camera just blinks rapidly. I'm not sure what's going on here. The camera works just fine when plugged into my Windows PC (which I'm trying to leave in the dust!!). When plugged in, the open as dialogue appears. Why the trouble on my Mac?