GNOME Bugzilla – Bug 733792
Several XFCE applications appear unresponsive after communicating with a daemon
Last modified: 2014-07-29 21:36:18 UTC
Several programs have a daemon mode call gtk_init() before fork()ing. This is unsafe, and when it goes wrong this will typically manifest as the daemon hanging shortly after forking, and appearing to simply do nothing at all. Please, check this bug is not affecting pixbuf.
I don't see the relation to gdk-pixbuf here