through my programming experience, my guess is that there isn't any "keyUp" function. i have confirmed this here: http://livedocs.adobe.com/flash/9.0/main…
i suggest you use "if(!Key.isDown(Key.DOWN))" the exclamation mark means "not", meaning "if the DOWN key is not down..."
also, you could use the onKeyUp event to listen for when the key is released
Common sense maybe helps in this one:
Key.isDown(Key.DOWN) <---- Key.isDown(...) means if it's pressed, Key.DOWN I bet it's the DOWN ARROW. So to check if DOWN ARROW is released you would: if(Key.isUp(Key.DOWN))
"Key.isDown" is a function that checks if a key is actually physically being pressed down, and "Key.DOWN" refers to the down arrowkey. So a key that is not being pressed would be like "if(Key.isUp(Key.DOWN))"