Hi , I have a Late 2010 MBA , and sometimes it just doesn't turn on. I shut it down , then , sometimes , in the next day , it just doesn't turn on. It have already happened 3 times. I shut the MBA down , then in the next day , it doesn't turn on. I took it to Apple Store twice , and when I took there , it would just turn on. Last time it happened , I connected the charger and waited about 20 minutes , and then , tried to turn on , and it worked. Whenever I turn it off , I've never let the battery down to 50% , always let it about 60%-70% , so it has nothing to do with the MBA being out of battery. Please help me , what's going on???