drapes fails to start/crashes on start

Whenever I try to run the desktop drapes program, nothing happens.

terminal output -

sagaci@uneti:~$ drapes
Exception in Gtk# callback delegate
  Note: Applications can use GLib.ExceptionManager.UnhandledException to handle the exception.
System.DllNotFoundException: libX11.so
  at (wrapper managed-to-native) Egg.TrayIcon:XInternAtom (intptr,string,bool)
  at Egg.TrayIcon.OnRealized () [0x00000] in <filename unknown>:0
  at Gtk.Widget.realized_cb (IntPtr widget) [0x00000] in <filename unknown>:0
   at GLib.ExceptionManager.RaiseUnhandledException(System.Exception e, Boolean is_terminal)
   at Gtk.Widget.realized_cb(IntPtr widget)
   at Gtk.Widget.gtk_widget_show_all(IntPtr )
   at Gtk.Widget.ShowAll()
   at Drapes.AppletWidget.CreateNotifyIcon()
   at Drapes.AppletWidget..ctor(AppletStyle style, Nullable`1 size)
   at Drapes.DrapesApp..ctor(System.String[] args)
   at Drapes.DrapesApp.Main(System.String[] args)

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: drapes 0.5.2-3.2
ProcVersionSignature: Ubuntu 2.6.38-8.42-generic 2.6.38.2
Uname: Linux 2.6.38-8-generic x86_64
Architecture: amd64
Date: Mon Jul 25 23:57:58 2011
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427.1)
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=en_AU:en
 LANG=en_AU.UTF-8
 SHELL=/bin/bash
SourcePackage: drapes
UpgradeStatus: No upgrade log present (probably fresh install)