Rotation and movement?

Hey guys. I'm still learning Unity, using JavaScript. I'm trying to make a character that you rotate with the left, and right, arrow keys, and then you press up, and he moves forward. I kind of have it working, but not quite. The problem is, once you rotate around so much, then the character starts moving in a different direction, than he is facing. I don't really know how to explain it better than that, other than the direction he is moving, and the direction he is facing, is not matching up. Here's the code

 #pragma strict
 var walkSpeed : int;
 var runSpeed : int;
 var turnSpeed : int;

 function Update ()
 {
 if (Input.GetKey(KeyCode.LeftArrow)) {
     transform.Rotate(0,-turnSpeed  * Time.deltaTime * turnSpeed,0);
 }
 
 if (Input.GetKey(KeyCode.RightArrow)) {
     transform.Rotate(0,turnSpeed  * Time.deltaTime * turnSpeed,0);
 }
 
 var direction = transform.forward * Time.deltaTime * walkSpeed;
 if (Input.GetKey(KeyCode.UpArrow)) {
     transform.Translate(direction);
 }
 }

I've even tried removing the " Time.deltaTime turnSpeed" But it's just the same result. Any help would be appreciated.