|Is your Nook(?) seeing the wifi signal (seeing the SSID)?|
Are you entering the access-key/password correctly for the wifi remember letters are case-senstive; and a zero may be a letter O and visa versa.
Also is there any other form of security enabled on your wifi router?
Do you know how to login to your router's home page? Generally wiser to do that via a cat-5/ethernet connection.