update-manager crashed with RuntimeError in <module>()

[chowder]

Binary package hint: update-manager

This is the output of the terminal.
Ubuntu 8.04 LTS

root@desktop:~# update-manager
/var/lib/python-support/python2.5/gtk-2.0/gtk/__init__.py:72: GtkWarning: could not open display
  warnings.warn(str(e), _gtk.Warning)
Traceback (most recent call last):
  File "/usr/bin/update-manager", line 43, in <module>
    gtk.init_check()
RuntimeError: could not open display

ProblemType: Crash
Architecture: i386
Date: Thu May 15 22:48:07 2008
DistroRelease: Ubuntu 8.04
ExecutablePath: /usr/bin/update-manager
InterpreterPath: /usr/bin/python2.5
Package: update-manager 1:0.87.27
PackageArchitecture: all
ProcCmdline: /usr/bin/python2.5 /usr/bin/update-manager
ProcEnviron:
 SHELL=/bin/bash
 PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
 LANG=en_US.UTF-8
PythonArgs: ['/usr/bin/update-manager']
SourcePackage: update-manager
Title: update-manager crashed with RuntimeError in <module>()
Traceback:
 Traceback (most recent call last):
   File "/usr/bin/update-manager", line 43, in <module>
     gtk.init_check()
 RuntimeError: could not open display
Uname: Linux 2.6.24-17-generic i686
UserGroups: