Turn off the computer, and unplug it
Press and hold the power button for 10 seconds.
Plug machine back in.
Press the power button.
Hold down command option PR on boot.
Hold these down until the machine reboots, let go of keys.
Plug in 1 device (mouse or keyboard)
Test All of the ports!™
Plug in device one at a time.
try to figure out of a certain device is causing the problem
If the SMC reset suggested by identd works, but the ports stop working again or you experience other strange behavior, you might want to have it diagnosed at your nearest Genius Bar - I just had the same problem plus a host of others and am getting the logic board replaced. Not saying that this is your problem, but if it persists despite the SMC reset, you should have it checked.