execption after resizing and unloading

GMBitmap.Bitmap = (GraphicsMill.Bitmap)GdiToGmBitmap(origGDIBmp);


        private GraphicsMill.Bitmap GdiToGmBitmap(System.Drawing.Bitmap GdiBitmap) {
            // bmpFloor is an .net bmp object
            // create the new aurigma bitmap
            GraphicsMill.BitmapClass gmBitmap = new GraphicsMill.BitmapClass();

            // copy the info
            MemoryStream memStream = new MemoryStream();
            GdiBitmap.Save(memStream, System.Drawing.Imaging.ImageFormat.Bmp);
            gmBitmap.LoadFromMemory(memStream.GetBuffer());

            // dont need the floor ms-bmp anymore
            GdiBitmap.Dispose();

            return gmBitmap;
        }