David, were you able to fix it? I chatted with Apple for over an hour and they suggested resetting my PRAM and my SMC. I did both, and haven't experienced the problem again yet. Worth a try.
"What we need to do to reset the SMC is make sure the computer is plugged in and charging before shutting down the computer completely. While it is powered off, we will need to hold the Shift, Control, and Option keys on the bottom left hand corner of the keyboard as well as the power button for about 5-10 seconds. After holding these keys for 5-10 seconds, we can let go of the buttons and power on your computer normally. You will not notice anything happening on the computer during the reset, which is normal, as long as the computer does not restart while holding the keys the process completed normally.
To reset the PRAM on your computer, you will want to shut down the computer. Before restarting it, you will want to locate the Command, Option, P, and R keys on your keyboard. Once you do that, power on the computer and hold those 4 keys on the keyboard before the grey screen, and the startup chime. You will want to hold those keys until the computer restarts twice, or you hear the chime and see the grey screen twice. After that, you can release the keys and use your computer as normal."
Hope this helps!