My MBP does not boot reliably. I have a 2.16GHz 15 inch core 2 duo MBP that developed a problem recently. It boots 50% of the time correctly but sometimes the screen does not come on. I hear the Superdrive making its usual noise after I press the power button but the screen remains blank -- no bang sound and no blue screen and no apple logo. The way I have been getting it to boot is by removing all power sources (AC adapter and battery) and let the MBP sit cold for...