Windows Phone 8: MediaLibrary Invalid Operation Exception

Question

I'm developing a Windows Phone 8 app, that takes all pictures from the library of the device and displays them at a listbox. But when I run it sometimes an error pops up that says: An exception of type 'System.InvalidOperationException' occurred in Microsoft.Xna.Framework.ni.dll but was not handled in user code

Any suggestion?

My code is:

    Dim notes As New List(Of Note)

    Dim m As New MediaLibrary
    Dim whatnumber As Integer = m.Pictures.Count

    TextBlock2.Text = whatnumber.ToString + " IMAGES"

    Dim imagesources As ImageSource()
    ReDim imagesources(whatnumber)

    Dim counter As Integer = 1
    For Each pic In m.Pictures

        imagesources(counter) = PictureDecoder.DecodeJpeg(pic.GetThumbnail)
        notes.Add(New Note With {.ImageName = imagesources(counter), .Title = counter.ToString})
        counter = counter + 1

    Next

    ListBox1.ItemsSource = notes