Strange error in using ThumbnailFactory::create()

[Liangxu Wang <wlx mygis org>]

Hi,
	I want to load the file's thumbnail, so Gnome::UI is used. The program
can be compiled without any error, but can not start, with error:
--------------
GLib-ERROR **: The thread system is not yet initialized.
aborting...
--------------
Code like this:

#include <gtkmm.h>
#include <libgnomeuimm.h>
----<snip>---
	Glib::RefPtr<Gdk::Pixbuf> thumbnail;
	Glib::RefPtr<Gnome::UI::ThumbnailFactory > th;
//error with this line
th=Gnome::UI::ThumbnailFactory::create(Gnome::UI::THUMBNAIL_SIZE_NORMAL);
	thumbnail=th->generate_thumbnail(uri,"application/pdf");
	if (thumbnail)		return thumbnail;
----<snip>---
	So what's the problem here?
	Thanks.
Sincerely yours,
Liangxu Wang