OS X: Low power alert with USB Devices, USB Keyboard, and USB SuperDrive
An alert may appear when USB devices are connected to your Mac's keyboard and an Apple USB SuperDrive is attached to the computer: "A USB device needs more power."
When you're using these devices together, plug them directly into the Mac's USB ports instead of the keyboard. This prevents the low alert from appearing. You can also plug your devices into a powered USB hub to avoid this message.
Alternatively, simply disconnect the Apple USB SuperDrive from the computer while the USB devices are plugged into the keyboard.