Description of problem: Segfault when cancelling RHN configuration. 

Version-Release number of selected component (if applicable): beta3.

How reproducible: Both times tried.

Steps to Reproduce:
1. Go through firstboot to RHN set up.
2. "Yes, I want to subscribe".
3: alt-N to 'Next'
3. When configuration dialogue box comes up, hit Cancel.
    
Actual results:

Left with blank X scree with mouse pointer. On control-alt-backspace back to text, 
get many error messages. Not sure where the to start, so including everything on 
the screen.  The precise line numbers changed the second time, but the error
messages
are the same.

(firstboot.py:3848): GLib-GObject-WARNING **: invalid uninstantiatable type 
'<unknown>' in cast to 'GtkOjbject'

(firstboot.py:3848): GLib-GObject-WARNING **: instance of invalid
non-instantiatable type '<unkown>'

(firstboot.py:3848): GLib-GObject-CRITICAL: file gsignal.c: line 2056
 (g_signal_handlers_destroy): assertion 'G_TYPE_CHECK_INSTANCE 
(instance)' failed.
/usr/sbin/firstbook: like 4:   3848 Segmentation fault 
/usr/bin/python2.2 /usr/share/firstbook/firstbook.phy $*

Expected results: On hitting cancel on the configuration for RHN, 
should return to the RHN "Yes, I want to subscribe"/"No, I do not"
choice. 

Additional info:

 1: The line numbers the second time: (firstboot.py: 3941) for all bits
     at the starts of lines; and 2056 remained the same.

 2: What on earth is uninstantiatable? :) 

Marked as high because it's pretty easy to do this, and it's a nasty result.