I agree with Mrsam; if your flux capacitor is out of wack, the sleep detector will not function properly. If his suggestion of the P, Z and Q keys doesn't work, I suggest taking your unit to an Apple Authorized Service Provider, and having a professional work on your machine. Please mention that it maybe the flux capacitor, as it will help to speed up the repair. If you've damaged the flux capacitor (instead of it needing a simple reset), then you will need to replace it - and it is a very expensive part.Well, your flux capacitor may be out of line. If you restart holding the P, Z and Q keys, it should start to work again.