I am on my second MacBook now; both have had the same problem with the up arrow key. When pressing the up arrow key with the same force as the other arrow keys, is does not always respond. To reproduce this, open any app that has a vertical scroll bar. Press the down arrow key a few times, then press the up arrow key a few times. I notice that unless I press the up arrow key about twice as hard as normal, I get about a 50% response. In addition, the up arrow key is the only key that I can depress fully, but softly and get no response. Can anyone confirm this issue? I am worried that since this has happend on two new MacBooks, it may be a systematic problem. Edit: This is a black MacBook.