I have this problem with my keyboard, Some keypress combinations are not being detected by my system.
While holding UP and LEFT arrow keys when I press the E key, it doesn't work. To be more precise I am playing FIFA and PES 12 with my keyboard and when I press the E key to pass in the Top left (UP+LEFT arrow) direction of screen, the keypress is not detected and the pass not executed.
Similarly , "S" doesn't work with DOWN+RIGHT, "A" with DOWN+LEFT etc.
To confirm the problem I tried same combinations in notepad and the result is same, they don't work.