Error when trying to start Wrowser

When trying to start Wrowser I get the following error:

/var/lib/python-support/python2.5/gtk-2.0/gtk/__init__.py:72: GtkWarning: could not open display
  warnings.warn(str(e), _gtk.Warning)
/usr/lib/python2.5/site-packages/matplotlib/backends/backend_gtk.py:40: GtkWarning: gdk_cursor_new_for_display: assertion `GDK_IS_DISPLAY (display)' failed
  cursors.MOVE : gdk.Cursor(gdk.FLEUR),
Traceback (most recent call last):
  File "/local3/MUE/ans/myOpenWNS/wrowser/bin/wrowser", line 35, in <module>
    import wrowser.Windows
  File "/local3/MUE/ans/myOpenWNS/wrowser/wrowser/Windows.py", line 42, in <module>
    import scenario.plotterFactory
  File "/local3/MUE/ans/myOpenWNS/wrowser/wrowser/scenario/plotterFactory.py", line 30, in <module>
    import generic
  File "/local3/MUE/ans/myOpenWNS/wrowser/wrowser/scenario/generic.py", line 29, in <module>
    from pylab import *
  File "/usr/lib/python2.5/site-packages/pylab.py", line 1, in <module>
    from matplotlib.pylab import *
  File "/usr/lib/python2.5/site-packages/matplotlib/pylab.py", line 292, in <module>
    from matplotlib.pyplot import *
  File "/usr/lib/python2.5/site-packages/matplotlib/pyplot.py", line 37, in <module>
    new_figure_manager, draw_if_interactive, show = pylab_setup()
  File "/usr/lib/python2.5/site-packages/matplotlib/backends/__init__.py", line 24, in pylab_setup
    globals(),locals(),[backend_name])
  File "/usr/lib/python2.5/site-packages/matplotlib/backends/backend_gtkagg.py", line 10, in <module>
    from matplotlib.backends.backend_gtk import gtk, FigureManagerGTK, FigureCanvasGTK,\
  File "/usr/lib/python2.5/site-packages/matplotlib/backends/backend_gtk.py", line 40, in <module>
    cursors.MOVE : gdk.Cursor(gdk.FLEUR),
RuntimeError: could not create GdkCursor object