diff -uNr calibre.old/src/calibre/gui2/ui.py calibre/src/calibre/gui2/ui.py
--- calibre.old/src/calibre/gui2/ui.py	2011-12-30 17:12:37.909499254 +0100
+++ calibre/src/calibre/gui2/ui.py	2011-12-30 17:14:33.899450513 +0100
@@ -681,7 +681,8 @@
         if write_settings:
             self.write_settings()
         self.check_messages_timer.stop()
-        self.update_checker.terminate()
+        if hasattr(self, 'update_checker') and self.update_checker:
+            self.update_checker.terminate()
         self.listener.close()
         self.job_manager.server.close()
         self.job_manager.threaded_server.close()
diff -uNr calibre.old/src/calibre/gui2/update.py calibre/src/calibre/gui2/update.py
--- calibre.old/src/calibre/gui2/update.py	2011-12-30 17:12:37.910499245 +0100
+++ calibre/src/calibre/gui2/update.py	2011-12-30 17:14:11.307655638 +0100
@@ -122,11 +122,11 @@
 
     def __init__(self, opts):
         self.last_newest_calibre_version = NO_CALIBRE_UPDATE
-        if not opts.no_update_check:
-            self.update_checker = CheckForUpdates(self)
-            self.update_checker.update_found.connect(self.update_found,
-                    type=Qt.QueuedConnection)
-            self.update_checker.start()
+        #if not opts.no_update_check:
+        #    self.update_checker = CheckForUpdates(self)
+        #    self.update_checker.update_found.connect(self.update_found,
+        #            type=Qt.QueuedConnection)
+        #    self.update_checker.start()
 
     def recalc_update_label(self, number_of_plugin_updates):
         self.update_found('%s%s%d'%(self.last_newest_calibre_version, VSEP,