为什么组件突然不能在VS2008里显示按钮图片了呢？求高手指点！


继承自BUTTOM
public partial class MButton : Button
    {
        static Bitmap bitmapNormal = Resources.btn_normal;
        static Bitmap bitmapHeighHight = Resources.btn_heightlight;
        static Bitmap bitmapFocus = Resources.btn_focus;
        static Bitmap bitmapPush = Resources.btn_focus;        private Bitmap bitmapBackGround = bitmapNormal;
        [Browsable(true), Category("Local"), Description("默认显示图像")]
        public Bitmap ImgBackGround
        {
            get { return bitmapBackGround; }
            set
            {
                bitmapBackGround = value;
                this.Invalidate();
            }
        }        public MButton()
        {
            InitializeComponent();
        }        private Bitmap _imgNormal = bitmapNormal;
        [Browsable(true), Category("Local"), Description("正常显示图像")]
        public Bitmap ImgNormal
        {
            get { return _imgNormal; }
            set { _imgNormal = value; this.Invalidate(); }
        }        private Bitmap _imgHeighLight = bitmapHeighHight;
        [Browsable(true), Category("Local"), Description("高亮图像")]
        public Bitmap ImgHeighLight
        {
            get { return _imgHeighLight; }
            set { _imgHeighLight = value; this.Invalidate(); }
        }        private Bitmap _imgFocus = bitmapFocus;
        [Browsable(true), Category("Local"), Description("聚焦图像")]
        public Bitmap ImgFocus
        {
            get { return _imgFocus; }
            set { _imgFocus = value; this.Invalidate(); }
        }        private Bitmap _imgPush = bitmapPush;
        [Browsable(true), Category("Local"), Description("鼠标按下图像")]
        public Bitmap ImgMouseDown
        {
            get { return _imgPush; }
            set { _imgPush = value; this.Invalidate(); }
        }        #region
        private string _Text;
        [Browsable(true), Category("Local"), Description("Text")]
        public string BtnText
        {
            get { return _Text; }
            set { _Text = value; }
        }        private Font _TextFont = new Font("宋体", 9f);
        [Browsable(true), Category("Local"), Description("Font")]
        public Font TextFont
        {
            get { return _TextFont; }
            set { _TextFont = value; }
        }        private Color _TextColor = Color.Black;
        [Browsable(true), Category("Local"), Description("FontColor")]
        public Color FontColor
        {
            get { return _TextColor; }
            set { _TextColor = value; }
        }
        #endregion        bool mousedown = false;
        bool mouseUpDown = false;
        private void MButton_MouseDown(object sender, MouseEventArgs e)
        {
            this.bitmapBackGround = _imgPush;
            this.Invalidate();
            mousedown = true;
            mouseUpDown = true;
        }        private void MButton_MouseEnter(object sender, EventArgs e)
        {
            this.bitmapBackGround = _imgHeighLight;
            this.Invalidate();
        }        private void MButton_MouseLeave(object sender, EventArgs e)
        {
            if (mousedown == false)
            {
                this.bitmapBackGround = _imgNormal;
                this.Invalidate();
            }
            else
            {
                this.bitmapBackGround = _imgFocus;
                this.Invalidate();
            }
        }        private void MButton_MouseUp(object sender, MouseEventArgs e)
        {
            this.bitmapBackGround = _imgHeighLight;
            this.Invalidate();
            mouseUpDown = false;
        }        private void MButton_Leave(object sender, EventArgs e)
        {
            this.bitmapBackGround = _imgNormal;
            this.Invalidate();
            mousedown = false;        }        private void MButton_Enter(object sender, EventArgs e)
        {
            this.bitmapBackGround = _imgFocus;
            this.Invalidate();
            mousedown = true;
        }        private void MButton_Paint(object sender, PaintEventArgs e)
        {
            Graphics g = e.Graphics;
            Bitmap tmpBitmap = new Bitmap(bitmapBackGround, this.Size);
            g.DrawImage(tmpBitmap, new PointF(0, 0));
            SizeF size = g.MeasureString(_Text, this.TextFont);
            if (mouseUpDown == false)
            {
                g.DrawString(_Text, this.TextFont, new SolidBrush(_TextColor), new PointF((this.Width - size.Width) / 2, (this.Height - size.Height) / 2));
            }
            else if (mouseUpDown == true)
            {
                g.DrawString(_Text, this.TextFont, new SolidBrush(_TextColor), new PointF((this.Width + 2 - size.Width) / 2, (this.Height + 2 - size.Height) / 2));
            }        }
    }将此按钮组件拖放在PANEL或者其它容器中，显示不出按钮的背景。只能显示文字如：mButton1！如何解决？什么情况引起的.啊？原来都会显示出来的！