Why doesn't my keyboard work sometimes?

Wired keyboards are supposed to work. It may be something inside the keyboard.

My best guess is either the keyboard is faulty or the machine may need the SMC and PRAM reset.

SMC RESET

• Shut down the computer.
• Unplug the computer's power cord and all peripherals.
• Press and hold the power button for 5 seconds.
• Release the power button.
• Attach the computers power cable.
• Press the power button to turn on the computer.

PRAM RESET

• Shut down the computer.
• Locate the following keys on the keyboard: Command, Option, P, and R. You will need to hold these keys down simultaneously in step 4.
• Turn on the computer.
• Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.
• Hold the keys down until the computer restarts and you hear the startup sound for the second time.
• Release the keys.

I'm having the same problem. I took the steps noted to reset the SMC and PRAM but it's still not working.

The keyboard was working fine, there was a power outage and when I turned the computer back on the wired keyboard wasn't working. The iMac looks for the bluetooth keyboard by default and seems like it's not even attempting to locate a wired keyboard.

OS X 10.8.2