Since upgrading to xfce4-notifyd 0.4.0, my journal is spammed with hundreds of "gdk_window_get_origin: assertion 'GDK_IS_WINDOW (window)' failed" messages. This did not happen with earlier versions (0.3.6 was the latest before 0.4.0) Seems that a new message is logged every time a new notification is sent - you can see that my monitoring the journal while using "notify-send" from a terminal.
This has been fixed in git master already and will be in the 0.4.1 release. *** This bug has been marked as a duplicate of bug 13935 ***
Sorry about the duplicate. I did a search before filing, but 13935 did not show up in the results because it had already been fixed (default search is for open bugs)