Three bugs ?

[yjh]

<UserControl x:Class="SilverlightApplication1.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    d:DesignHeight="600" d:DesignWidth="800">

    <UserControl.Resources>

        <Style TargetType="Button">

            <Setter Property="Width" Value="180"/>

        </Style>

    </UserControl.Resources>

    <!--<ScrollViewer VerticalAlignment="Top" HorizontalScrollBarVisibility="Auto">-->

        <telerik:RadGridView x:Name="TestRadGV"
            telerik:StyleManager.Theme="Office_Blue" RowIndicatorVisibility="Collapsed"
            AutoGenerateColumns="False" ShowGroupPanel="False" CanUserReorderColumns="False"
            CanUserResizeColumns="False" CanUserFreezeColumns="False">

            <telerik:RadGridView.Columns>

                <telerik:GridViewDataColumn Header="1"
                    DataMemberBinding="{Binding Name}" MinWidth="200" Width="0.275*"/>

                <telerik:GridViewDataColumn Header="2"
                    DataMemberBinding="{Binding DName}" MinWidth="200" Width="0.275*"/>

                <telerik:GridViewDataColumn Header="3"
                    DataMemberBinding="{Binding Description}" MinWidth="300" Width="0.45*"/>

                <telerik:GridViewDataColumn>

                    <telerik:GridViewDataColumn.CellTemplate>

                        <DataTemplate>

                            <TextBlock Text="Test" HorizontalAlignment="Center"/>

                        </DataTemplate>

                    </telerik:GridViewDataColumn.CellTemplate>

                </telerik:GridViewDataColumn>

            </telerik:RadGridView.Columns>

        </telerik:RadGridView>

    <!--</ScrollViewer>-->

</UserControl>

using System.Collections.Generic;
using System.Windows.Controls;

namespace SilverlightApplication1
{
    public class Item
    {
        public string Name { get; set; }

        public string DName { get; set; }

        public string Description { get; set; }
    }

    public partial class MainPage : UserControl
    {
        public MainPage()
        {
            InitializeComponent();

            var items = new List<Item>();

            items.Add(new Item
            {
                Name = "1",

                DName = "1",

                Description = "1"
            });

            items.Add(new Item
            {
                Name = "2",

                DName = "2",

                Description = "2"
            });

            items.Add(new Item
            {
                Name = "3",

                DName = "3",

                Description = "3"
            });

            TestRadGV.ItemsSource = items;
        }
    }
}

Just run above codes, you will find:

1.  One column header line will disappear when iexplorer window width maximized or changed.It is a old issue:
http://www.telerik.com/community/forums/silverlight/gridview/radgridview-add-an-extra-column-at-the-end.aspx#1742535

2.  Using implicit style on button will make GridView's filter button not rightmost. The filter button must define width property explicitly.

3   If uncomment ScrollViewer code, will get a very long GridView. RadGridView has a wrong behavior to process a star value of width property, look this thread:
http://www.telerik.com/community/forums/silverlight/gridview/scrolling-behavior-gridview-in-docking-inside-scrollviewer.aspx