My USB ports are acting up. One port doesn't work at all and the second port only charges my devices. I'm trying to transfer files, pic's, music etc. from my cellphone to my computer then to my USB but it's giving me a message: Because a USB device was drawing too much power from your computer, one or more of your USB devices have been disabled. I have a MacBook Pro 13-inch Late 2011. Can someone please help me out???