I have been having boot issues lately with my Macbook Pro. It takes multiple times to boot, it'll just stay as a white screen and have to turn it off and on multiple times to boot into OSX. Sometimes it'll just display a flashing folder with a question mark. Also, when I am finally into OSX, if I close the lid and come back and try to use it from standby mode it'll have just have that circle rainbow icon and have to power down and try to boot it again. I have tried replacing with a SSD but doing the same thing. Could it be the HDD cable to the motherboard? It is not under warranty so trying to avoid having to pay Apple to fix it.