Message not being recieved

I have a gameobject, and two images: the inventory, the inventory slot, and the slot icon image.
The inventory sends a message to the slot every update:

		item1 = inv[0];
		Slot1.SendMessage ("recieveContentData", item1);
		item2 = inv[1];
		Slot2.SendMessage ("recieveContentData", item2);
		item3 = inv[2];
		Slot3.SendMessage ("recieveContentData", item3);
		item4 = inv[3];
		Slot4.SendMessage ("recieveContentData", item4);

The slot receives this message:

	public void receiveContentData(Item newContents)
		contents = newContents;

And then, every update, tells the slot icon to change it’s image to that of the item, contents.

		if (contents != null)
			itemImage.enabled = true;
			itemImage.sprite = contents.itemsprite;
			itemImage.sprite = null;
			itemImage.enabled = false;

The problem is, when I run this script, apparently there is no receiver to this message;
Even though I assigned all of the Slot variables to gameobjects with the slot script attached, and all of the slots have a Slot icon image as children. Here is the exact error message:

SendMessage recieveContentData has no receiver!
UnityEngine.GameObject:SendMessage(String, Object)

Check the spelling of Receiver - The I and E are different in the send message and the function - assuming the code has been copy/pasted?