Set display picture of StoredContact from byte[] - windows-phone-8

Question

I have a byte[] containing picture data. I want to set this picture data as a display picture of a StoredContact in windows phone 8. I have tried:
byte[] data = ...
ContactStore store = await ContactStore.CreateOrOpenAsync(ContactStoreSystemAccessMode.ReadWrite, ContactStoreApplicationAccessMode.ReadOnly);
StoredContact contact = await store.FindContactByRemoteIdAsync(remoteId);
using (IInputStream stream = new MemoryStream(data).AsInputStream())
{
await contact.SetDisplayPictureAsync(stream);
}
but i get System.UnauthorizedAccessException on the AsInputStream()-call. I have the ID_CAP_CONTACTS-capability set and the contact belongs to a custom data store, to which i have write access. Anyone know how to solve this?
EDIT:
I get the data from a web request, using the following to extract the byte data:
DataContractJsonSerializer serializer = new DataContractJsonSerializer(new PhotoObject().GetType());
var result = (PhotoObject)serializer.ReadObject(stream);
byte[] data = Convert.FromBase64String(result.Data);
[DataContract]
class PhotoObject
{
[DataMember(Name = "size")]
public string Size { get; set; }
[DataMember(Name = "data")]
public string Data { get; set; }
}

Answer 1

I finally managed to get around this problem. The first thing I did was to create the stream using:
new MemoryStream(data, 0, data.Length, true, true).AsInputStream();
instead of
new MemoryStream(data).AsInputStream();
This got rid of the UnauthorizedException, however it gave me an ArgumentException: "Value does not fall within the expected range" on the SetDisplayPictureAsync-call instead. I still do not know why it works, but i got around this by writing the data to temporary file, which I then open and pass to SetDisplayPictureAsync. This is my code for doing this:
//Write bytes to file then open file and pass stream to setdisplaypicture.
StorageFolder localFolder = ApplicationData.Current.LocalFolder;
var folder = await localFolder.CreateFolderAsync("Photo_Temp_Folder", CreationCollisionOption.OpenIfExists);
var file = await folder.CreateFileAsync("photo_" + contact.Id, CreationCollisionOption.ReplaceExisting);
uint written = 0;
using (var writeStream = await file.OpenAsync(FileAccessMode.ReadWrite))
{
while (written < data.Length)
{
written += await writeStream.WriteAsync(data.AsBuffer());
}
}
using (var accessStream = await file.OpenAsync(FileAccessMode.Read))
{
await contact.SetDisplayPictureAsync(accessStream);
await contact.SaveAsync();
}
await file.DeleteAsync();
Hope it helps someone.