I'm having a problem with the code below. When I run it the progress bar will pulse for around 10 secs as meant to and then move on to downloading and will show the progress but when finished it will not move on to the next step it just locks up.

import sys
import time
import pygtk

import gtk

import gobject

import threading
import urllib
import urlparse

class WorkerThread(threading.Thread):



    def __init__ (self, function, parent, arg = None):

        threading.Thread.__init__(self)

        self.function = function

        self.parent = parent

        self.arg = arg

        self.parent.still_working = True



    def run(self): # when does "run" get executed?

        self.parent.still_working = True

        if self.arg == None:

            self.function()

        else:

            self.function(self.arg)

        self.parent.still_working = False    



    def stop(self):

        self = None

class MainWindow:
    def __init__(self):
        gtk.gdk.threads_init()

        self.wTree = gtk.Builder()

        self.wTree.add_from_file("gui.glade")
        self.mainWindows()


    def mainWindows(self):

        self.mainWindow = self.wTree.get_object("frmMain")

        dic = { 

            "on_btnNext_clicked" : self.mainWindowNext,

        }

        self.wTree.connect_signals(dic)


        self.mainWindow.show()

        self.installerStep = 0 # 0 = none, 1 = preinstall, 2 = download, 3 = install info, 4 = install

        #gtk.main()

        self.mainWindowNext()

    def pulse(self):
        self.wTree.get_object("progress").pulse()


        if self.still_working == False:

            self.mainWindowNext()

        return self.still_working

    def preinstallStep(self):
        self.wTree.get_object("progress").set_fraction(0)
        self.wTree.get_object("btnNext").set_sensitive(0)
        self.wTree.get_object("notebook1").set_current_page(0)
        self.installerStep = 1
        WT = WorkerThread(self.heavyWork, self) #Would do a heavy function here like setup some thing

        WT.start()



        gobject.timeout_add(75, self.pulse)

    def downloadStep(self):
        self.wTree.get_object("progress").set_fraction(0)
        self.wTree.get_object("btnNext").set_sensitive(0)
        self.wTree.get_object("notebook1").set_current_page(0)
        self.installerStep = 2
        urllib.urlretrieve('http://mozilla.mirrors.evolva.ro//firefox/releases/3.6.3/win32/en-US/Firefox%20Setup%203.6.3.exe', '/tmp/firefox.exe', self.updateHook)

        self.mainWindowNext()

    def updateHook(self, blocks, blockSize, totalSize):
        percentage = float ( blocks * blockSize ) / totalSize
        if percentage > 1:
            percentage = 1

        self.wTree.get_object("progress").set_fraction(percentage)

        while gtk.events_pending():

            gtk.main_iteration()

    def installInfoStep(self):
        self.wTree.get_object("btnNext").set_sensitive(1)
        self.wTree.get_object("notebook1").set_current_page(1)
        self.installerStep = 3

    def installStep(self):
        self.wTree.get_object("progress").set_fraction(0)
        self.wTree.get_object("btnNext").set_sensitive(0)
        self.wTree.get_object("notebook1").set_current_page(0)
        self.installerStep = 4

        WT = WorkerThread(self.heavyWork, self) #Would do a heavy function here like setup some thing

        WT.start()



        gobject.timeout_add(75, self.pulse)

    def mainWindowNext(self, widget = None):
        if self.installerStep == 0:
            self.preinstallStep()
        elif self.installerStep == 1:
            self.downloadStep()
        elif self.installerStep == 2:
            self.installInfoStep()
        elif self.installerStep == 3:
            self.installStep()
        elif self.installerStep == 4:
            sys.exit(0)

    def heavyWork(self):
        time.sleep(10)

if __name__ == '__main__':
    MainWindow()
    gtk.main()