Does anyone else's new iMac (2012 27") bring up a warning box when the machine wakes from sleep if a device is left plugged in? I opted for the wired keyboard as the usb ports allow me to conveniently charge my 4s while I work, but I've had a warning dialogue tell me that a USB device is drawing too much power and the USB has been shut down. If the machine is awake, I can plug my phone in and it's ok so it seems to be something associated with going to sleep. Anyone ?????