My MacBook sometimes has trouble waking from sleep correctly. I have to press the power button a few seconds, then once more (shortly) and it will wake from what I think is hibernation. There are a couple of rounded rectangles on an otherwise gray screen, near the bottom of the screen, making up a progress bar. When all rectangles are full, my MacBook is usable again. Sometimes, it won't wake at all, leaving me with no other option than to restart it. Really annoying.
Anyone else experiencing this problem? What could be causing it?