MacBook looses keyboard responsiveness and then dies - I had the same experience almost a week ago, My MacBook (13.3 inch Early 2008) (MB402LL/A) Model No. A1181 suddenly lost keyboard responsiveness and then wouldn't power up at all.
I ordered a replacement upper case/keyboard that just arrived today, After installing it I followed '''mayer's''' advice and Remove the battery and unplug it, then press the power button for five seconds.
Then after putting the battery back in pressed the power button and it works perfectly fine now. I guess the keyboard chip suddenly died, It is a used MacBook that I bought a few weeks ago.