I just bought a 13.3" macbook pro. I already got one that had a dead pixel on the screen that I had to return. Now when I use this one, and I lay my hands on the palm rests while typing, sometimes when I move my hands to use the track pad, I feel vibrations as I move my hand across it. When I close the lid and run my hands over the top of it, I also can intermittently pick up vibrations. Is this normal? What could be causing it? If it's not normal do you think it's a problem w/ the power adapter? It seems to only happen when plugged in.