I have an external HDD that has two usb connections for power and data. most of the time my macbook pro doesn't detect it and I have to keep unplugging and plugging into different usb ports and then it gets detected after a while. I tried the same HDD with a windows desktop and it worked well. Is this because HDD not getting enough power ? Are all usb ports the same when it come to power? any ideas to get this working? Thanks.