Pressing buttons without huge pauses?

Hi. I’m creating 2d adventure game with Actionscript 3.
I’ve created square where my hero can travel inside. Hero moves from left to right and it even jumps and hits.

There is this tiny error which I would like to get rid off. If I press up and left my guy will go up… huuuge pause… then it starts to go left. It’s really irritating.

Can you guys help me?

Here is the code.
stage.addEventListener(KeyboardEvent.KEY_DOWN, checkKeysDown);
function checkKeysDown(event: KeyboardEvent):void{
Keys(event);
}
function Keys(event: KeyboardEvent):void {
if (event.keyCode == Keyboard.LEFT) {
heroface = true;
hero.x-=playerSpeed;
}
if (event.keyCode == Keyboard.RIGHT) {
heroface = false;
hero.x+=playerSpeed;
}
if (event.keyCode == Keyboard.UP) {
hero.y-=20;
falling = false;
fall(falling);
}
if (event.keyCode == Keyboard.CONTROL) {
hitting = true;
if (heroface == true) {
hero.gotoAndStop(3);
}
else {
hero.gotoAndStop(4);
}

 }

}

You can see the game here.