invoke throw exception

Question

Dear all,

I have below code but don't know why when idle for somethime, the below code throw exception.

Do you know how to solve it??

beginCB = new beginPOSCallBack(beginPOS);

public void init()
{
 try
 {
  this.Invoke(beginCB, new object[] { ErrorVO.OK });
// Invoke or BeginInvoke cannot be called on a control until the window handle has been created.
 at System.Windows.Forms.Control.MarshaledInvoke(Control caller, Delegate method, Object[] args, Boolean synchronous)
   at System.Windows.Forms.Control.Invoke(Delegate method, Object[] args)
   at login.init()

 }
 catch(Exception ex)
 {
  //write log
 }
....
}