Keys "Y" "H" and "N" stopped working on wired aluminum keyboard

The "Y" "H" and "N" suddenly stopped working on my wife's wired, aluminum, iMac keyboard which is about 2.5 years old. She typed an e-mail and the keys worked--she then started a Word Doc and the keys would not respond. There were no spills, but it has been very humid here for two months here in Athens GA. The machine is covered by Apple Care which, I think would, replace the keyboard, but is there any home remedy to try before taking to the local Apple store? Thanks