I just noticed a few times, that when I push the sleep button on my surface, the colors are inverted for a fraction of a second. This happens in the short period between pushing the button and the screen is going off. Do I have to worry? Because 1-2 times per week also the after waking up the device, there is a "graphic driver restored" message... I think it's just a driver issue, who knows? (In addition, as mentioned in the othe post, the device wont turn on after opening the keyboard cover. I have to push for a few seconds the sleep button and wait to restart)