diff -uNr calibre.old/src/calibre/gui2/ui.py calibre/src/calibre/gui2/ui.py
--- calibre.old/src/calibre/gui2/ui.py	2011-06-26 19:51:17.912975862 +0200
+++ calibre/src/calibre/gui2/ui.py	2011-06-26 19:52:21.156346644 +0200
@@ -647,7 +647,7 @@
         if write_settings:
             self.write_settings()
         self.check_messages_timer.stop()
-        self.update_checker.terminate()
+        # 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	2011-06-26 19:51:17.913975852 +0200
+++ calibre/src/calibre/gui2/update.py	2011-06-26 19:56:50.608665533 +0200
@@ -121,13 +121,13 @@
 
 class UpdateMixin(object):
 
-    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()
+    #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()
 
     def recalc_update_label(self, number_of_plugin_updates):
         self.update_found('%s%s%d'%(self.last_newest_calibre_version, VSEP,