Inconsistent WWW stream behaviour

Does anybody perhaps have any clues as to why this from the docs is working fine (script attached to cube):

#pragma strict
var newTexture = "http://my.site/my.png";
function Start () {
}

function Update () {
	transform.Rotate(0, 5*Time.deltaTime, 0);
	if(Input.GetKey ("1") ) 
	{ 
	switchTexture();
	}

}


function switchTexture() {
		var www : WWW = new WWW (newTexture);
		 yield www;
		 renderer.material.mainTexture = www.texture;
}

But this (attached to the FPS camera) gives me a could not connect to host error:

#pragma strict

function Start () {

}
var metalTexture = "http://my.site/mypic.png";
function doTextureGUI(){
	Debug.Log("Loading texture from the web");
	var www : WWW = new WWW (metalTexture);
	yield www;
	var cube = GameObject.Find("PreviewCube");
	cube.renderer.material.mainTexture = www.texture;
}

function OnGUI() {
  if (GUI.Button(Rect(10,70,150,60),"Switch Texture"))
  {
      doTextureGUI();
  }
}
function Update () {

}

I am using the latest Unity Pro and I have set my build target to Windows Standalone.
Any help much appreciated. This is my first Unity script! :slight_smile:

Can nobody help me?