I had the same problem with keydown().
the keycode that should be processed if I pressed the END - key in the simulator has the value: 0x00120000 , but the value of Keypad.KEY_END is 0x00000012.
The solution I was told is to convert the keycode:
int keyValue = Keypad.key( keycode );
if (keyValue == Keypad.KEY_END)
//... DO SOMETHING ...