Some of us had this discussion last spring; it is not a platform issue, but definitely hardware related (assuming the PT is ok). As Drozd said, be sure to avoid use of an unpowered USB hub, plug directly into the Mac USB port (which it sounds like you are doing). If one port doesn't work, try another, and/or unhook other USB powered
devices from the Mac such as printers and external hard drives. USB ports are powered from the board, but they really aren't setup to pump out much more than 1A of current, and you should have at least 2A - this can vary from computer to computer, model to model, depending on the motherboard power controller. The best option is to get a powered USB hub, there are several options you can find on Amazon et.al., although the current specs can be hard to find sometimes.
