Multithreading Beginner question - Forms

Question

Hello all, 

Been reading for some time now and thought I'd post a quickie. 

Why can I not open an instance of a form from within a child thread?

I can open it when not using multi threading so why can't I use threading to open a separate form?

The aim is to have one main form (form2) to do a DB update and a clock form (Clock) to display some graphics that will spiral around to show the processing time. 

Please help. 

Many thanks. 

Dan.  

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Text;

using System.Windows.Forms;

using System.Threading;

namespace WindowsApplication5

{

    public partial class Form2 : Form

    {

        Thread thread1;        

        private bool _stopThreads = false;

        public Form2()

        {

            InitializeComponent();

        }

        private void Form2_Load(object sender, EventArgs e)

        {

            thread1 = new Thread(new ThreadStart(DisplayThread1));

        }

        private void GO_Click(object sender, EventArgs e)

        {

 

             thread1.Start();             

        }

        void DisplayThread1()

        {

                Clock ClockForm = new Clock();

                ClockForm.Show();            

        }

    }

}