Disabling Ethernet Prevents Mac OS X From Waking

Problem: When MacBook lid is closed, fan continues to spin and MacBook becomes very hot.

Description: When in use the MacBook fan behaves as expected. On closing the lid to put the MacBook sleep, the fan continues to spin and the base of the machine becomes very hot.

Opening the lid displays a black screen. No mouse or login screen displayed. Fan continues to spin at what seems to be maximum RPM. Closing the lid again does not stop the fan from spinning.

Only available option is to hold the power button to shut down the system.

On pressing the power button to restart the system, the MacBook starts, displays grey start up screen for a second or two and then restarts automatically. MacBook then starts normally.

Once the user logins, the system works as normal again. Putting the system to sleep, causes the problem to reoccur.

Solution: The user deactivated the Ethernet interface within System Preferences -> Network. Reactivating the Ethernet interface and restarting the machine resolved the problem.

(Who’d have thought that disabling the Ethernet interface would prevent the system from sleeping? Certainly not me when I decided to do so.)