It works for very little time, but after about 2 minutes it crashes

Just when I start it, it works: I attach and detach devices, and notification works nicely. But if I wait for a couple of minutes, and then try to attach/detach any device, it crashes. Here's output (I started it multiple times here)

OS: Linux Mint 13 MATE

dimon@dimon-progr ~/download $ udev-notify
Traceback (most recent call last):
  File "./udev-notify.py", line 319, in <module>
    notification.show()
glib.GError: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name :1.1061 was not provided by any .service files
dimon@dimon-progr ~/download $ udev-notify
Traceback (most recent call last):
  File "./udev-notify.py", line 319, in <module>
    notification.show()
glib.GError: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name :1.1065 was not provided by any .service files
dimon@dimon-progr ~/download $ udev-notify
Traceback (most recent call last):
  File "./udev-notify.py", line 319, in <module>
    notification.show()
glib.GError: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name :1.1069 was not provided by any .service files
dimon@dimon-progr ~/download $ udev-notify
Traceback (most recent call last):
  File "./udev-notify.py", line 319, in <module>
    notification.show()
glib.GError: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name :1.1073 was not provided by any .service files