Spawn Script on Y axis not working!!!?

Can someone please help me with my spawn script. I have a spawn script attach to a cube placed in my game that spawn prefabs on that cube (stretched out) but on the X axis, when I try to place the same script on a cube on the Y axis , the prefabs just spawn at the same place and not randomly on the cube. Could somebody help me , so that the cube on the Y axis spawns randomly on the cube (stretch out) and not at the same place. Thank you Here's my script:

 #pragma strict 
 // Variable to store the enemy prefab 
 public var enemy : GameObject; 
 // Variable to know how fast we should create new enemies 
 public var spawnTime : float = 2; 
 function Start() { 
 // Call the 'addEnemy' function every 'spawnTime' seconds 
 InvokeRepeating("addEnemy", spawnTime, spawnTime); 
 } // New function to spawn an enemy 
 function addEnemy() { 
 // Variables to store the X position of the spawn object 
 // See image below 
 var x1 = transform.position.x - GetComponent.<Collider>().bounds.size.x/2; 
 var x2 = transform.position.x + GetComponent.<Collider>().bounds.size.x/2; 
 // Randomly pick a point within the spawn object 
 var spawnPoint = new Vector2(Random.Range(x1, x2), transform.position.y); 
 // Create an enemy at the 'spawnPoint' position 
 Instantiate(enemy, spawnPoint, Quaternion.identity);
 }