Grid with SharedSizeGroup columns is acting very weird (*NOT* infinite loop)

If you run the sample window below the upper ItemsControl will update layout for several seconds until finally all columns will have the correct width (correct = identical to the columns inside the lower ItemsControl).

You can change the width of the window and scroll the lower ItemsControls surrounding ScrollViewer both horizontally and vertically -- but as soon as you change the height of the Window the layout will flip for several seconds.

Note: There is no sizing ambiguity like in other questions where the grid infinitely updates sizes.

Is it me doing something wrong -- and if so, how could I fix this? -- or should I post this problem to Microsoft-Connect?

Code behind:

namespace DynamicGridColumnBinding
{
    using System;
    using System.Collections.Generic;
    using System.Globalization;
    using System.Linq;
    using System.Windows;
    using System.Windows.Controls;

    public partial class MainWindow
    {
        private static readonly CultureInfo[] cultureInfos =
            CultureInfo.GetCultures(CultureTypes.NeutralCultures).Take(15).ToArray();

        public MainWindow()
        {
            this.InitializeComponent();
        }

        public static IEnumerable<CultureInfo> AllCultures
        {
            get { return cultureInfos; }
        }

        private void GridInitialized(object sender, EventArgs e)
        {
            var grid = (Grid)sender;
            for ( int i = 0; i < cultureInfos.Length; i++ )
                grid.ColumnDefinitions.Add(new ColumnDefinition
                    {
                        Width = GridLength.Auto,
                        SharedSizeGroup = "g" + i,
                    });
        }

        private void ScrollViewerScrollChanged(object sender, ScrollChangedEventArgs e)
        {
            if ( e.HorizontalChange != 0 )
                this.legendScroller.ScrollToHorizontalOffset(e.HorizontalOffset);
        }
    }
}