I am really new to the FLASH and Actionscript. I am making this simple game where you control a small spacecraft with keys. The problem is that, if I keep pressed one of the buttons (UP/DOWN/LEFT/RIGHT) for more than 2 seconds, FPS suddenly drops from 60 to below 40. But that's not all. If I press another key, while holding that LEFT/RIGHT/WHATEVER key down, fps quickly jumps back to stable 60. Any ideas why? PS I have a boolean array where I keep track which keys are pressed and released.

This is class I use for keyboard input management. I found it somewhere on the web, though it is very simple.

// Key.aspackage {       import flash.display.Stage;    import flash.events.Event;    import flash.events.KeyboardEvent;	import flash.ui.Keyboard;       /**     * The Key class recreates functionality of     * Key.isDown of ActionScript 1 and 2. Before using     * Key.isDown, you first need to initialize the     * Key class with a reference to the stage using     * its Key.initialize() method. For key     * codes use the flash.ui.Keyboard class.     *     * Usage:     * Key.initialize(stage);     * if (Key.isDown(Keyboard.LEFT)) {     *    // Left key is being pressed     * }     */    public class Key {               private static var initialized:Boolean = false;  // marks whether or not the class has been initialized        private static var keysDown:Object = new Object();  // stores key codes of all keys pressed        /**         * Initializes the key class creating assigning event         * handlers to capture necessary key events from the stage         */        public static function initialize(stage:Stage) {            if (!initialized) {                // assign listeners for key presses and deactivation of the player                stage.addEventListener(KeyboardEvent.KEY_DOWN, keyPressed);                stage.addEventListener(KeyboardEvent.KEY_UP, keyReleased);                stage.addEventListener(Event.DEACTIVATE, clearKeys);                // mark initialization as true so redundant                // calls do not reassign the event handlers                initialized = true;            }        }               /**         * Returns true or false if the key represented by the         * keyCode passed is being pressed         */        public static function isDown(keyCode:uint):Boolean {            if (!initialized) {                // throw an error if isDown is used                // prior to Key class initialization                throw new Error("Key class has yet been initialized.");            }            return Boolean(keyCode in keysDown);        }               /**         * Event handler for capturing keys being pressed         */        private static function keyPressed(event:KeyboardEvent):void {			// create a property in keysDown with the name of the keyCode            keysDown[event.keyCode] = true;        }               /**         * Event handler for capturing keys being released         */        private static function keyReleased(event:KeyboardEvent):void {            if (event.keyCode in keysDown) {                // delete the property in keysDown if it exists                delete keysDown[event.keyCode];            }        }               /**         * Event handler for Flash Player deactivation         */        private static function clearKeys(event:Event):void {            // clear all keys in keysDown since the player cannot            // detect keys being pressed or released when not focused            keysDown = new Object();        }    }}

And then, every frame I check the keyboard state like this:

	        // I call for Key.initialize(stage); earlier        if (Key.isDown(Keyboard.LEFT))         auto.rotation-=turn_angle;	else if (Key.isDown(Keyboard.RIGHT))		auto.rotation+=turn_angle;	else if (Key.isDown(Keyboard.UP))		speed+=acceleration;	else if (Key.isDown(Keyboard.DOWN))	{				speed-=acceleration;				if (speed<0)			speed = 0;				}