ClipBoard.SetImage (passing bmp of Control rect) causes other controls to disappear

Question

I've created a method, both capture controls and put them into the ClipBoard as BMP images. The problem is that when you call it from, say, a UserControl with some buttons in it, and, say, a Chart control of some type, it captures the Chart Control just fine, but the buttons in the UserControl disappear. Very odd.

Any ideas?

 using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace ClipTest
{
    ///<summary>
    /// Provides methods to copy a Control or UserControl to the Windows clipboard as a BMP
    ///</summary>
    public class CopyToClipBoard
    {
        private string _ErrorMessage = string.Empty;
        
        /// <summary>
        /// Public property, which stores any Exception message encountered during capture
        /// </summary>
        /// <remarks>
        /// If CopyControlToClipboard returns false, check this property
        /// </remarks>
        public string ErrorMessage
        {
            get { return _ErrorMessage; }
            set { ErrorMessage = _ErrorMessage; }
        }

        /// <summary>
        /// Allows copying of a Control's screen area to the clipboard as a BMP
        /// </summary>
        /// <param name="ControlToCapture">
        /// A Control, which is captured to the clipboard entirely
        /// </param>
        /// <example>
        /// Calling this method to capture a Control
        /// <code>
        /// 
        /// CopyToClipBoard ctc = new CopyToClipBoard();
        /// bool bCopied;
        /// bCopied = ctc.CopyControlToClipboard(ControlName);
        ///
        /// </code>
        /// </example>
        /// <permission cref="System.Security.PermissionSet">
        /// Everyone can access this method.
        /// </permission>
        public bool CopyControlToClipboard(Control ControlToCapture)
        {
            try
            {
                // Get dimensions of the Control we are to capture
                Size renderSize = ControlToCapture.RenderSize;
                // Create a RenderTargetBitmap of the same dimensions to store the capture
                RenderTargetBitmap rtb = new RenderTargetBitmap((int)renderSize.Width, (int)renderSize.Height, 96, 96, PixelFormats.Pbgra32);

                // Render a white background in Clipboard
                Rectangle vRect = new Rectangle()
                {
                    Width = ControlToCapture.RenderSize.Width,
                    Height = ControlToCapture.RenderSize.Height,
                    Fill = Brushes.White
                };
                vRect.Measure(renderSize);
                vRect.Arrange(new Rect(renderSize));
                rtb.Render(vRect);

                // Grab the Control area to a RenderTargetBitmap
                ControlToCapture.Measure(renderSize);
                ControlToCapture.Arrange(new Rect(renderSize));
                rtb.Render(ControlToCapture);

                // And finally, put it in the Clipboard
                Clipboard.SetImage(rtb);
                return true;
            }
            catch (Exception ex)
            {
                // Set the ErrorMessage property for caller to check after false return
                _ErrorMessage = ex.ToString();
                return false;
            }
        }

        /// <summary>
        /// Allows copying of a UserControl's screen area to the clipboard as a BMP
        /// </summary>
        /// <param name="UserControlToCapture">
        /// A UserControl, which is captured to the clipboard entirely
        /// </param>
        /// <example>
        /// Calling this method from within the UserControl to capture
        /// <code>
        /// 
        /// CopyToClipBoard ctc = new CopyToClipBoard();
        /// bool bCopied;
        /// bCopied = ctc.CopyControlToClipboard(this);
        ///
        /// </code>
        /// </example>
        /// <permission cref="System.Security.PermissionSet">
        /// Everyone can access this method.
        /// </permission>
        public bool CopyControlToClipboard(UserControl UserControlToCapture)
        {
            try
            {
                // Get dimensions of the Control we are to capture
                Size renderSize = UserControlToCapture.RenderSize;
                // Create a RenderTargetBitmap of the same dimensions to store the capture
                RenderTargetBitmap rtb = new RenderTargetBitmap((int)renderSize.Width, (int)renderSize.Height, 96, 96, PixelFormats.Pbgra32);

                // Render a white background in Clipboard
                Rectangle vRect = new Rectangle()
                {
                    Width = UserControlToCapture.RenderSize.Width,
                    Height = UserControlToCapture.RenderSize.Height,
                    Fill = Brushes.White
                };
                vRect.Measure(renderSize);
                vRect.Arrange(new Rect(renderSize));
                rtb.Render(vRect);

                // Grab the Control area to a RenderTargetBitmap
                UserControlToCapture.Measure(renderSize);
                UserControlToCapture.Arrange(new Rect(renderSize));
                rtb.Render(UserControlToCapture);

                // And finally, put it in the Clipboard
                Clipboard.SetImage(rtb);
                return true;
            }
            catch (Exception ex)
            {
                // Set the ErrorMessage property for caller to check after false return
                _ErrorMessage = ex.ToString();
                return false;
            }
        }
    }
}