I just replaced my early 2011 15" MBP with a late 2011 one. I use it with a 30" Apple Display that requires a Dual Link DVI adapter, which plugs in to one of the USB ports. On my early 2011 model, I could use either USB port. On my new one, I can only use the front one. Does this mean Apple revised the power on the USB ports between the early and late 2011 models?