Answer to "standby light glowing but not starting up"i have same problem with my macbook pro 15'. it starts only after i heat it for some time with hair dryer without doing so it wont start at all.
Answer to "Logic board or left I/O board problem?"I have same problem. My macbook pro starts only after heating it by forcing it to start with dc power for several hours, but under normal condition when i press the power button the fans start, HD powers up, so does Super drive but only for a few seconds. I had the logic board replaced a few months ago because the screen didn't turn on, now this problem is really turning me mad. :-(