i got the replacement of my MB one month ago due to the random shut down problem. the symptom before the replacement was not only random shut down but also that the MB could not be turned on once a while. now it's been one month after i got the replacement from apple store, there is no randon shutdown at all, but when i got up this morning, i couldn't turn it on. i tried several times, but it just turned out to be dead. any suggestion about what i'm supposed to do? shall i ask for a refund or a replacement? i'm just afraid of that i would get a defect model again.