[XML Serialization] Crashes application ?

        // -- Create the Chunk.
        /// <summary>
        /// Creates the Chunk at the Cooardinate and returns the string..
        /// </summary>
        /// <param name="?"></param>
        private string CreateChunk(int ChunkX, int ChunkY)
        {
            // -- Create a stream writer.
            StreamWriter _Writer = new StreamWriter(Path + ChunkX + "_" + ChunkY + ".txt");
 
            // -- Create a new Chunk.
            Chunk _Chunk = new Chunk(ChunkX, ChunkY, ChunkSize, ChunkSize);
 
            // -- Generate the Chunk.
            for (int x = 0; x < ChunkSize; x++)
            {
                for (int y = 0; y < ChunkSize; y++)
                {
                    // -- Block.
                    byte Block = ID.BLOCK_AIR;
                    if (ChunkY == 0 && y > ChunkSize / 2)
                        Block = ID.BLOCK_GRASS;
 
                    // -- Set the Block.
                    _Chunk.SetBlockID(x, y, Block);
                }
            }
 
            // -- Get the XML string.
            string _ReturnString;
            _ReturnString = SerializeToString(_Chunk);
 
            // -- Write.
            _Writer.Write(_ReturnString);
 
            // -- Close the Writer.
            _Writer.Flush();
            _Writer.Close();
 
            // -- Return.
            return _ReturnString;
        }

        public static T SerializeFromString<T>(string xml)
        {
            XmlSerializer serializer = new XmlSerializer(typeof(T));
 
            using (StringReader reader = new StringReader(xml))
            {
                return (T)serializer.Deserialize(reader);
            }
        }
 

        public static string SerializeToString(object obj)
        {
            XmlSerializer serializer = new XmlSerializer(obj.GetType());
 
            using (StringWriter writer = new StringWriter())
            {
                serializer.Serialize(writer, obj);
 
                return writer.ToString();
            }
        }

    [Serializable]
    public class Chunk
    {
        // -- Blocks.
        private Block[,] _Blocks;
 
        // -- Cooardinates.
        public int X { get; set; }
        public int Y { get; set; }
 
        // -- Chunk.
        /// <summary>
        /// Initializes a new Chunk based on the Width and Height given.
        /// </summary>
        /// <param name="Width"></param>
        /// <param name="Height"></param>
        public Chunk(int X, int Y, int Width, int Height)
        {
            // -- Create the Block List.
            _Blocks = new Block[Width, Height];
 
            // -- Create all the Blocks.
            for (int i = 0; i < Width; i++)
            {
                for (int j = 0; j < Height; j++)
                {
                    // -- Create a new block.
                    Block _Block = new Block(ID.BLOCK_AIR);
 
                    // -- Add the block.
                    _Blocks[i,j] = _Block;
                }
            }
        }
 
        // -- Set a Block.
        /// <summary>
        /// Sets the block in the Chunk.
        /// </summary>
        /// <param name="X">X of the block.</param>
        /// <param name="Y">Y of the block.</param>
        /// <param name="ID">The ID of the block.</param>
        public void SetBlockID(int X, int Y, byte ID)
        {
            // -- Set the Block.
            _Blocks[X, Y].ID = ID;
        }
 
        // -- Get a block.
        /// <summary>
        /// Returns the ID of the given block.
        /// </summary>
        /// <param name="X">The X of the Block.</param>
        /// <param name="Y">The Y of the Block.</param>
        public byte GetBlockID(int X, int Y)
        {
            // -- Return.
            return _Blocks[X, Y].ID;
        }
    }

    [Serializable]
    public static class ID 
    {
        public static int BlockSize = 32;
 
        public const byte BLOCK_AIR = 30;
        public const byte BLOCK_DIRT = 31;
        public const byte BLOCK_GRASS = 32;
    }
 
    [Serializable]
    public class Block
    {
        public byte ID { get; set; }
 
        // -- Block
        /// <summary>
        /// Initializes a new Block with the ID given.
        /// </summary>
        /// <param name="_ID">The ID of the block.</param>
        public Block(byte _ID)
        {
            // -- Set the ID.
            ID = _ID;
        }
    }