Cannot Detect All Key pressed onKeyDown

Here is the code I used:

var keyListener:Object = new Object();
keyListener.onKeyDown = function() {
    trace("DOWN -> Code: " + Key.getCode() + "	ACSII: " + Key.getAscii() + "	Key: " + chr(Key.getAscii()));
 if (Key.getCode() == 65) {
        trace ("Virtual key code: "+Key.getCode()+" 65");

It is an usual code to listen the key presed on the keyboard. For some reason, I cannot detect any letter-key exept letters “w”, “x”, “d” and “J”. I tested it on a different computer and results are the same. It is driving me crazy. I am not sure what is the problem. Is anybody experienced the same? Is any work around it? Thank you!