Description of problem:
This small program:

==>
#!/usr/bin/python
import gtk.gdk
gtk.gdk.threads_init()
a = gtk.FileChooserButton ('title')
<==

often gives assertion failures, and occasionally terminates abnormally.

The assertion failure output looks like this:

==>
test.py:4: Warning: IA__g_object_new_valist: object class `GThemedIcon' has no
property named `names'
  a = gtk.FileChooserButton ('title')

(test.py:8759): GLib-GIO-CRITICAL **: g_themed_icon_constructed: assertion
`themed->names != NULL && themed->names[0] != NULL' failed
<==

or sometimes like this:

==>
./test.py:4: Warning: IA__g_object_new_valist: object class `GThemedIcon' has no
property named `names'
  a = gtk.FileChooserButton ('title')

(test.py:8935): GLib-GIO-CRITICAL **: g_themed_icon_constructed: assertion
`themed->names != NULL && themed->names[0] != NULL' failed

(test.py:8935): GLib-GIO-CRITICAL **: g_themed_icon_constructed: assertion
`themed->names != NULL && themed->names[0] != NULL' failed

(test.py:8935): GLib-CRITICAL **: g_strv_length: assertion `str_array != NULL'
failed
<==

while the abort output looks like this:

==>

GLib-GObject-ERROR **: g_type_plugin_*() invalidly modified type `GThemedIcon'
aborting...
<==

This test case was distilled from system-config-printer, and this bug has the
effect of occasionally causing that program to occasionally abort.

Version-Release number of selected component (if applicable):
glib2-2.16.3-5.fc9.x86_64

How reproducible:
About 40% of the time.

Steps to Reproduce:
1. ./test.py
  
Actual results:
Assertions, errors, mayhem.

Expected results:
No output, normal exit.

Additional info:
Works fine in Fedora 8.