Return an array of objects from a REST enabled WCF service

I am returning a complex type from my WCF service (which is hosted in SharePoint 2010) and I wan to be able to return an array (or collection of some type) as a property.
The aim is to have a generic Type that contains standard stuff like Error, Message and an array of Data.
On the server I am using proper types and only want the array of objects to be returned in the JSON.
It works fine if I return an collection of the real type...but casting to objects causes a login challenge (which seem weird) and even as the admin...I can't get past it.

    public class MyServiceReponse
 {
     public List<string> Errors { get; set; }
     public List<string> Messages { get; set; }
     public bool Success { get; set; }
     public int DataCount { get; set; }
     public object[] ResponseData { get; set; }
     public IEnumerable<MyOtherType> Sites { get; set; }
 
     public MyServiceReponse()
     {
         Errors = new List<string>();
         Messages = new List<string>();
         Success = true;
     }
 
     public void AddError(Exception ex)
     {
         Success = false;
         Errors.Add("Oooops, there seems to be a problem. (" + ex.Message + ")");
     }
 }    
 public class MyOtherType
     {
         public string Name { get; set; }
         public string Ticker { get; set; }
         public string Other { get; set; }
     }
 

How would I go about achieving this?
First I though I would just have ResponseData as an object...setting my collection to it...but that doesn't work either.
Thx

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