use of gtk in a nautilus extension

[Nils]

Hi,
I am having some trouble opening a simple message/dialog to the user
from a natilus extension..

I have written a simple nautilus extension using python. It adds one
MenuItem to the context menu.
for testing I wanted to open a simple dialog when the user clicks this
menuitem.
(The code can be found - with some nice formatting here:
http://stackoverflow.com/questions/3325772/use-gtk-in-a-nautilus-extension-using-python)

The code is as follows:
--- cut ---
import gtk
import nautilus
import os
def alert(message):
    """A function to debug"""
    dialog = gtk.MessageDialog(None, gtk.DIALOG_MODAL,
gtk.MESSAGE_INFO, gtk.BUTTONS_CLOSE, message)
    dialog.run()
    dialog.destroy()

class TestExtension(nautilus.MenuProvider):
    def __init__(self):
        pass

    def get_file_items(self, window, files):
        items = []
        """Called when the user selects a file in Nautilus."""
        item = nautilus.MenuItem("NautilusPython::test_item", "Test",
"Test")
        item.connect("activate", self.menu_activate_cb, files)
        items.append(item)
        return items

    def menu_activate_cb(self, menu, files):
        """Called when the user selects the menu."""
        for name in files:
            alert(name)
--- cut ---

When I click on the menuitem nothing happens...
But when I replace def alert(message) like this:
def alert(message):
    """A function to debug"""
    easygui.msgbox(message)
and obviously drop import gtk and add import easygui,

The dialog does appear. Can someone tell me why this is ??

Yours,
Nils