On
RightToLeft cultures, the popup from UXStackButton is displayed outside of the
view area, although there is space available to display it. 
Please check the following example:
<Intersoft:UXPage 

	xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
	xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
	xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
	xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
	mc:Ignorable="d"
	xmlns:Intersoft="http://intersoft.clientui.com/schemas"
	x:Class="ClientUIApplication2.MainPage" 
	Title="MainPage Page"
	d:DesignWidth="640" d:DesignHeight="480">
	
	<Grid x:Name="LayoutRoot" FlowDirection="RightToLeft">
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="70"></ColumnDefinition>
            <ColumnDefinition Width="*"></ColumnDefinition>
            <ColumnDefinition Width="70"></ColumnDefinition>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="*"></RowDefinition>
            <RowDefinition Height="*"></RowDefinition>
            <RowDefinition Height="*"></RowDefinition>
        </Grid.RowDefinitions>
        <Intersoft:UXStackButton Name="btnSettings" Content="Open Settings" DisplayMode="Content" StackMode="GridStyle" StackGridMode="DynamicGrid" 
                                 Width="50" Height="30" BorderBrush="Black" Margin="20,0,0,0" VerticalAlignment="Top">
            <Intersoft:UXStackButton.StackGridTemplate>
                <DataTemplate>
                    <Grid Width="250">
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="*"></ColumnDefinition>
                            <ColumnDefinition Width="*"></ColumnDefinition>
                        </Grid.ColumnDefinitions>
                        <Intersoft:GlassButton Content="Button 1" Margin="4"  Grid.Column="0"/>
                        <Intersoft:GlassButton Content="Button 2" Margin="4" Grid.Column="1"/>
                    </Grid>
                </DataTemplate>
            </Intersoft:UXStackButton.StackGridTemplate>
        </Intersoft:UXStackButton>
        <Intersoft:UXStackButton BorderBrush="Black" Content="Open Settings" DisplayMode="Content" Height="30"  Name="uXStackButton1" StackGridMode="DynamicGrid" StackMode="GridStyle" VerticalAlignment="Top" Width="50" Grid.Column="2">
            <Intersoft:UXStackButton.StackGridTemplate>
                <DataTemplate>
                    <Grid Width="250">
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="*" />
                            <ColumnDefinition Width="*" />
                        </Grid.ColumnDefinitions>
                        <Intersoft:GlassButton Content="Button 1" Grid.Column="0" Margin="4" />
                        <Intersoft:GlassButton Content="Button 2" Grid.Column="1" Margin="4" />
                    </Grid>
                </DataTemplate>
            </Intersoft:UXStackButton.StackGridTemplate>
        </Intersoft:UXStackButton>
    </Grid>
</Intersoft:UXPage>

The horizontal alignament is complelty wrong for the two buttons.

Also, the vertical alignament is wrong regardless of the FlowDirection - the popup should be opened below the buttons and the arrow should point to the buttons.

We are using ClientUI 5 SP1 for Silverlight 4.