Question about ClutterContent

[Unknown <ctthaler gmail com>]

Hi,

I'm trying to develop a program using clutter but I'm running into trouble.
I can define ClutterContent, set it into a clutter stage (gtk embedded) and that
works so far.

ClutterContent *frame;

frame = clutter_image_new ();
pixbuf = gdk_pixbuf_new_from_file (" ...

clutter_image_set_data (CLUTTER_IMAGE (frame), ... (pixbuf)

But if I want to change the image data in a different thread (g_thread_new) the
function (clutter_image_set_data) throws an error. I' cannot even define a new
frame.
Why is that so?