[debajyoti@dbera beagled]$ cat a.cs
using System;
using System.Net;

class abcd {
        public static void Main ()
        {
                HttpListener l = new HttpListener ();
                l.Prefixes.Add ("http://*:4000/foo/");
                l.Start ();
                l.Stop ();
                l.Start ();
                Console.Read ();
        }
}
[debajyoti@dbera beagled]$ gmcs -debug a.cs
[debajyoti@dbera beagled]$ mono --debug a.exe

Unhandled Exception: System.ObjectDisposedException: The object was used after being disposed.
  at System.Net.HttpListener.CheckDisposed () [0x0001c] in /home/mandrake/rpm/BUILD/mono-1.2.5/mcs/class/System/System.Net/HttpListener.cs:267
  at System.Net.HttpListener.Start () [0x00000] in /home/mandrake/rpm/BUILD/mono-1.2.5/mcs/class/System/System.Net/HttpListener.cs:239
  at abcd.Main () [0x00022] in /usr/share/devel/beagle-gnome/trunk/beagle/beagled/a.cs:11