Ios problem with www class

enter code herehey there I wanted to get a xml file from a webserver. It worked perfect for android and pc, but I can't get the connection on ios. I think ios got problems with the www class, but I also think its possible and I've got a mistake in the coroutine. Please have a look at my code, maybe youre able to help me:

Debug.Log("ERROR: " + www.error) shows me "ERROR: ".

crossdomin.xml is on the server

 void Start(){
    StartCoroutine(StartLoading());
 }
 
 IEnumerator StartLoading(){
    string url = "http://www.pixcube.com/games_ad/AppData.xml";
    WWW www = new WWW(url);
    while(!www.isDone)
       yield return null;

    if (www.error == null){
       XmlDocument xmlDoc = new XmlDocument();
       xmlDoc.LoadXml(www.data);
       ProcessAppLinks(xmlDoc.SelectNodes("AppLinks/AppLink"));
    }else{
       Debug.Log("ERROR: " + www.error);
    }    
 }
 
 private void ProcessAppLinks(XmlNodeList nodes){
    foreach (XmlNode node in nodes){
       //get all infos out of the xml node
       StartCoroutine(DownloadImage(nodeWithImageWebLink));
    }
 }
 
 IEnumerator DownloadImage(string url){
    WWW www = new WWW(url);
    while(!www.isDone)
       yield return null;
         
    imageArray.Add(www.texture);
 
 }