I experienced a similar similar problem: I have a DELL Inspiron N411z, and I was suddenly starting to receive a beep with any key I use. Another symptom was the fan running at high speed all time; you can notice that having a high windy noise towards the left of the laptop. Problem was the laptop was running in engineering mode (I don't know why it went into that mode). We discovered this because when restarting the machine, it was showing a message right in the beginning, saying something like: "Press Fn + X to change from Engineering Mode ..." we did it and now everything looks normal. No beeps in the keyboard and fan speed back to normal. Try re-booting your laptop and see if you find a similar message when machine is coming up.
