C# Array Index Out of Range

Hello.

I come from an AS3 background and the C# way of doing things is throwing me for a loop. I'm trying to create an array of transforms for a tile editor. Whenever I try to check if the transform is null I get an out of range exception. I'm guessing that I haven't initialized it, but it looks good when I compare it with the code on MSDN.

Here's the code in question. Any assistance would be greatly appreciated!

Editor.CS

 void UpdateTile ()
 {
     if (tile == null || !inRange)
         return;
 
     if (deleting)
     {
         if (map.instances[index] != null)
         {
             DestroyImmediate (map.instances[index].gameObject);
             map.instances[index] = null;
         }
     }
     else
     {
         if (map.instances[index] == null)
         { 
             var instance = Instantiate (tile) as Transform;
             instance.parent = ship.transform;
             instance.position = new Vector3 (cursorX * map.gSize, cursorY * map.gSize);
             map.instances[index] = instance;
         }
     }
 }

TileMap.CS

 public class TileMap: MonoBehaviour 
 {
     public float    gSize        = 1.0f;
     public int    gColumns    = 6;
     public int    gRows        = 6;
 
     public Transform[] instances = new Transform[1000];
 }