My macbook pro froze up one day, and since then it has taken 2,5 hours to start it up. I press the start button, the led in the front lights up, fans turn on, optical disc starts spinning a little, and nothing else happens. It just sits there for two hours and about 27 minutes with no activity and a black screen, and then it magically boots up just like normal. I've tried resetting the SMC and the NVRAM and the PRAM and all that with no success. I've even formated the harddrive and re-installed OS X. I also ran the apple hardware test, which said that everything was fine. I tried switching RAM with a friend of mines MBP, that did not help either. Any idea what's causing this?