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()

I have a feeling that its something to do with:

while gtk.events_pending():
    gtk.main_iteration()

Is there a better way of doing this?