No keys work (external keyboard)

§ Disconnect and reconnect your keyboard if it is external. Make sure that the connector is completely inserted into the port. (USB plugs fit into ports one way only, and won't allow you to make a connection if you try to connect them in upside-down.) Test the keyboard again.

§ Connect your keyboard to a different USB port.

§ Try a different keyboard on your computer if possible, or your keyboard on a different Mac.

Portable Mac's built-in keyboard only produces numbers (MacBook, MacBook Pro)

§ Make sure the Num Lock key is off, or not active.

Some keys don't work as expected

1.              Open Speech preferences in System Preferences. If "Speak selected text when the key is pressed" is enabled, the key combination to speak text cannot be used for other purposes or used to type text--change to a more obscure key combination (try to use more modifier keys such as Shift, Command, Option, and Control). Or, simply disable the "Speak selected text when the key is pressed" option.

2.              Open Universal Access preferences in System Preferences, click the Keyboard tab, and make sure that Slow Keys is turned off. With Slow Keys on, you need to press a key for a longer period of time for it to be recognized.

3.              In Universal Access preferences, click the Mouse tab, and make sure Mouse Keys is turned off. With Mouse Keys enabled, you cannot use the Numeric Keypad to enter numbers--instead the keypad moves the pointer (cursor). (There is an option to enable Mouse Keys with five presses of the Option key; you may want to turn that option off to avoid accidentally enabling it.)

4.              If the issue persists, open System Preferences and click International.

5.              Click the Input Menu tab.

6.              Click the Keyboard Viewer "On" checkbox to select it.

7.              From the Input (flag) menu, choose Show Keyboard Viewer.

8.              If the keyboard is connected and detected by Mac OS X, the keys you type will highlight in the Keyboard Viewer window. Try typing to see which keys are not highlighting in Keyboard Viewer.

9.              Open TextEdit (or another text application) and try to type something using the keys that were previously not responding.