Flickering - Transparency and BackgroundImages

SetStyle(ControlStyles.SupportsTransparentBackColor | 
         ControlStyles.Opaque | 
         ControlStyles.UserPaint |
         ControlStyles.AllPaintingInWmPaint, true);

public partial class OpenNewPanel : System.Windows.Forms.Panel
{
    #region Members

    private const float TITLE_POINT_SIZE = 16;
    private const float DESCRIPTION_POINT_SIZE = 9;

    private Bitmap gradientBackground { get; set; }
    private Point titleLocation = new Point(156, 4);
    private Point descriptionLocation = new Point(161, 30);

    public string PanelTitle { get; set; }
    public string PanelDescription { get; set; }

    #endregion // Members

    /// <summary>
    /// Ctor
    /// </summary>
    public OpenNewPanel()
    {
        InitializeComponent();
        // Members
        this.PanelTitle = string.Empty;
        this.PanelDescription = string.Empty;
        // Styles
        SetStyle(ControlStyles.UserPaint | ControlStyles.OptimizedDoubleBuffer | ControlStyles.AllPaintingInWmPaint, true);
        // Misc
        InitializeBackgroundGradient();
        // Events
        this.MouseEnter += new EventHandler(OpenNewPanel_MouseEnter);
        this.MouseLeave += new EventHandler(OpenNewPanel_MouseLeave);
    }

    #region Overrides

    protected override void OnPaint(PaintEventArgs e)
    {
        base.OnPaint(e);
        //
        // --- Custom Paint Operations Below ---
        //
        //e.Graphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias;
        Graphics graphics = e.Graphics;
        Font titleFont = new Font("Microsoft Sans Serif", TITLE_POINT_SIZE , FontStyle.Bold, GraphicsUnit.Point);
        Font descriptionFont = new Font("Microsoft Sans Serif", DESCRIPTION_POINT_SIZE , FontStyle.Regular, GraphicsUnit.Point);
        StringFormat format = new StringFormat();
        format.Alignment = StringAlignment.Near;

        this.SuspendLayout();
        this.InvokePaintBackground(this, e);
        // Draw Title
        graphics.DrawString(this.PanelTitle, titleFont, new SolidBrush(Color.Black), (PointF)this.titleLocation);
        // Draw Description
        graphics.DrawString(this.PanelDescription, descriptionFont, Brushes.Black,
            new RectangleF(this.descriptionLocation.X, this.descriptionLocation.Y, this.Width - this.descriptionLocation.X - 10, this.descriptionLocation.Y + 100),
            format);
        this.ResumeLayout();
    }

    #endregion // Overrides

    #region Events

    /// <summary>
    /// Fires when the mouse enters the Open New Panel
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    private void OpenNewPanel_MouseEnter(object sender, EventArgs e)
    {
        SuspendLayout();
        this.BackgroundImage = this.gradientBackground;
        this.BackColor = Color.Transparent;
        ResumeLayout();
    }

    /// <summary>
    /// Fires when the mouse leaves the Open New Panel
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    private void OpenNewPanel_MouseLeave(object sender, EventArgs e)
    {
        SuspendLayout();
        this.BackgroundImage = null;
        this.BackColor = Color.Transparent;
        ResumeLayout();
    }

    #endregion // Events

    #region Methods

    /// <summary>
    /// Creates a Vertical DodgerBlue to White Gradient Bitmap
    /// </summary>
    private void InitializeBackgroundGradient()
    {
        System.Drawing.Drawing2D.LinearGradientBrush gradBrush;
        gradBrush = new System.Drawing.Drawing2D.LinearGradientBrush(
            new Rectangle { Height = this.Height, Width = this.Width }, Color.FromArgb(90, Color.DodgerBlue), Color.White, LinearGradientMode.Vertical);
        Bitmap bmp = new Bitmap(this.Width, this.Height);
        Graphics g = Graphics.FromImage(bmp);
        g.FillRectangle(gradBrush, new Rectangle(0, 0, this.Width, this.Height));
        this.gradientBackground = bmp;
    }

    #endregion // Methods
}