gtk_toggle_button_set_active()

[riboaz xs4all nl]

Yesterday I wrote about how I was suspecting problems related to hiding
and unhiding widgets and trying to use gtk_toggle_button_set_active(). 
Today, I have a deeper understanding.

There is, in fact, no relation to the widgets being hidden or not. 
(Thinking that there could be a relation, I attempted to use g_idle_add()
and a function that was only responsible for setting the widget once it
had actually been rendered on the screen.  But to no avail, no change in
non-responsiveness.)

And, it's spreading.  I created two more radio button groups, in a
completely different part of my application and again, using
gtk_toggle_button_set_active() does not work the second and subsequent
times (the first time it is called it does work!).

And, I have other radio buttons where this is not a problem, it's only
happening with radio buttons I have added to my code since a couple of
days ago.

So my questions change:
1) are there any circumstances/conditions in which a radio button
disallows itself being set by gtk_toggle_button_set_active()?  has anyone
else seen this behaviour?

2) what can i do to further analyze and track the origin of this problem
down?

3) I have considered that program memory is somewhere being corrupted, but
if this were the case, how would it be possible that the radio button
continues to work fine via the mouse?  (thus, i've concluded no memory
corruption could be the culprit.  is this, however, conclusive?)

I'm stuck and frustrated, any advice hugely appreciated.

richard boaz