If your computer immediately goes into hibernation after the initial start-up screen and will not wake here is a possible solution.
MacBook Pro (Early 2009) and later, all models of MacBook Air, and MacBook (Late 2009).
- Shut down the computer.
- Plug in the MagSafe power adapter to a power source, connecting it to the Mac if its not already connected.
- On the built-in keyboard, press the (left side) Shift-Control-Option keys and the power button at the same time.
- Release all the keys and the power button at the same time.
- Press the power button to turn on the computer.
Note: The LED on the MagSafe power adapter may change states or temporarily turn off when you reset the SMC.