Please describe the problem:
The script given in "Steps to reproduce" should end up quietly and peacefully.
However it ends up in an exception, even though all requested actions were indeed performed.
It ends up in an exception most of the time, but not always.

Steps to reproduce:
#!/usr/bin/env python
from ldtp import *

program_name = 'anjuta'
window_title = 'frm*Anjuta*'
dlgAnjutaPreferences = 'dlgAnjutaPreferences'

launchapp(program_name, env=1)
if not waittillguiexist(window_title):
	msg = 'Window does not exist'
	log(msg, error)
	raise LdtpExecutionError(msg)
#print window_title #debug	
selectmenuitem(window_title, 'mnuEdit;mnuPreferences')
wait(1) #In case the messages are not yet received

uncheck(dlgAnjutaPreferences, 'chkDonotloadlastsessiononstartup')
check(dlgAnjutaPreferences, 'chkDonotloadlastsessiononstartup')
uncheck(dlgAnjutaPreferences, 'chkDonotloadlastprojectandfilesonstartup')
check(dlgAnjutaPreferences, 'chkDonotloadlastprojectandfilesonstartup')
click(dlgAnjutaPreferences, 'btnClose')

#Quiting Anjuta...
selectmenuitem(window_title, 'mnuFile;mnuQuit')

Actual results:
GTK Accessibility Module initialized
Bonobo accessibility support initialized

(anjuta:8476): Gtk-CRITICAL **: gtk_button_leave: assertion `GTK_IS_BUTTON (button)' failed
Traceback (most recent call last):

+ Trace 212888

Expected results:
No messages on stderr.

Does this happen every time?
Most of the time, but not always.

Other information: