Same thing happened to me. Since I almost always used my Apple Bluetooth keyboard ANYWAY, I probably won't ever bother fixing it. If you can't find a cheap way to fix the built-in keyboard, look on eBay or Craigslist or just go to your local Best Buy or whatever and I'd recommend the actual Apple Bluetooth (wireless) keyboard. It's fantastic! But you could also pick up a cheap ($5-$15) USB-connected auxiliary keyboard at various discount stores, which you can usually just plug in and it should work immediately.
These solutions aren't ideal, but they're very quick, cheaper, and if you're like me, you'll prefer the Apple Bluetooth keyboard over the built-in keyboard ANYWAY...jst not quite as convenient to carry around with you, but it IS very slimline...not bulky or heavy AT ALL.