I just bought a 500gb WD MyBook Studio Edition External HD. When I plugged it in and powered it up it immediately popped up on my MBP (OS 10.4) and I easily backed up some files. However after I disconnected it I can't get it to connect w/ my Mac again. I've tried both the firewire 400 and 800 cords but nothing happens. I power it up then plug it in, plug it in then power. Anyone know whats goin on? I had a usb external and it would just pop up evertime I plugged it in.