Xml Databinding doesn't work on some computers

I've wrote some code with a xml databinding. On one machine with win7 32 bit it works perfectly, but on another with win7 64 bit not.

using System.Windows.Forms;
using System.Xml;

namespace DataBindingDemo {
    public partial class Form1 : Form {
        string xmlPath = Properties.Settings.Default.XmlPath;
        XmlDocument doc; 
   
        public Form1() {
            InitializeComponent();

            this.doc = new XmlDocument();
            this.doc.Load(xmlPath);
            XmlNodeList list = this.doc.GetElementsByTagName("test");
            XmlNode node1 = list[0];
            XmlNode node2 = list[1];

            Binding binding1 = new Binding("Text", node1, "InnerText");
            this.textBox1.DataBindings.Add(binding1);

            Binding binding2 = new Binding("Text", node2, "InnerText");
            this.textBox2.DataBindings.Add(binding2);

            this.FormClosed += new FormClosedEventHandler(Form1_FormClosed);
        }

        void Form1_FormClosed(object sender, FormClosedEventArgs e) {
            this.doc.Save(xmlPath);
        }
    }
}

Why?