Actually version 2.0.0f1 but you dont have it listed:

From: http://www.noesisengine.com/forums/viewtopic.php?f=3&t=1045

I have a TabControl with a Tabitem, as defined below:

[code]
<ListBox
x:Name="KeyBindingsList"
Height="Auto"
HorizontalAlignment="Stretch"
VerticalAlignment="Top"
ScrollViewer.HorizontalScrollBarVisibility="Disabled">
<ListBox.ItemTemplate>
<DataTemplate>
<UniformGrid Columns="2">
<Label Content="{Binding Path=Name}" VerticalAlignment="Center" />
<Button Content="{Binding Path=PrimaryKeyName}" />
</UniformGrid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
[/code]

When pressing the Button, the ListBox content shifts to the left. It also happens when the width of the ListBox is the same size as the container.