Since updating to 10.9.2 today, my iMac will not lock when I press the power button. It will still bring up the shut down menu if I press and hold. Anyone know anything about this?
I've since found the answer to this question at: https://discussions.apple.com/message/24997114#24997114. Press and hold the power button for 2 seconds to sleep, longer to bring up the shut down menu.