I had the same problem with a mid 2007 macbook pro running under Mavericks, i played some music on it on a friday noon, i went to the gim for about 1 hour, i did put the macbook pro in sleep modus, and when i got back from the gim and when i opened the lid of my computer, it wouldnt wake up anymore, i removed the power cord and battery, i tried to reboot this macbook pro, nothing, just a boing, and my screen stayed black, i tried everything, booted it up with the ram removed, only powercord, only battery, harddrive disconnected, and when i searched the web with my iphone, i realised it whas the GPU that failed, an Nvidia chip, i disassembled the complete macbook and i did a logic board reflow in the oven ad 200 degrees celcius for about 7.30 minutes, hoping and praying offcourse, and when i putted it back together . . . It jus booted up like nothing happened . . . Crazy, why is this happening to computers that costs SO much money? I have an old pc, with a Nvidia chip also and i had NEVER the kind of problem i had with my old macbook, now i am using a 17 inch macbook pro with a dual Nvidia chip and i am just scared that it would happen again over time so my fans are blowing ad full speed all the time, i clean out the dust once a month and i have a temp monitoring app and cpu activity monitor installed now . . . I hope that this macbook doesnt die on me . . .